Computer Graphics with Photoshop - Need help interpreting color test results

Author

Need help interpreting color test results

ronviers@gmail.com

2006-08-16, 6:21 am

I have a titanium white backdrop - perfectly white.
I painted my main light reflector, by mixing acrylics, so it lights the
backdrop neutral, that is, when I photograph the backdrop, in raw, and
load the image into RSE or ACR in Adobe RGB at 16 bit, I get a readout
of R=197,G=197,B=192 a tiny bit yellow I admit but I thought I could
live with that being tired of mixing paint. I have never used a D50
but I bet they are not much better than that.
Anyway, next I convert the raw image, to Tiff with RSE and PSD with
ACR, with no modifications in either converter, and open them with CS2.
I do this on two computers, my fast one and my slow one. My working
space is Adobe RGB and mode is 16 bit/channel. Both computers CS2
environments are identical and both use CRTs.
After the conversion I have both the Tiff and the PSD loaded on each
computer. I check the readouts at the several coordinates and get the
exact same reading on both the output from RSE and ACR - e.g., at
5000x3500, I get R=196,G=197,B=191. This is a surprise but also a
relief. I kinda thought they would convert them slightly differently.
Then I set CS2 to display the image of the converted raw file, the PSD,
in full screen preview. So now I have a Photoshop image of my raw file
displayed on the CRT. Then I set the original raw file still in the
camera as the source for the custom white balance setting for the
camera.
Next I photograph the Photoshop image at a quarter second to get
several screens of refreshed image.
Then I load that image back into RSE and ACR. So what do you think I
get? I thought I would get a nice neutral image possibly a little
yellow. But no! I get a very blue image. What could be going on? A
typical reading after the photo is R=56,G=87,B=143. Look how blue that
is. Can someone help me interpret these results? Shouldn't this be
a good test for checking the color moving through the system?

Thanks,
Ron

Mike Russell

2006-08-16, 6:21 am

<ronviers@XXXXXXXXXX> wrote in message
news:1155716764.359019.279410@m73g2000cwd.googlegroups.com...
>I have a titanium white backdrop - perfectly white.
> I painted my main light reflector, by mixing acrylics, so it lights the
> backdrop neutral, that is, when I photograph the backdrop, in raw, and
> load the image into RSE or ACR in Adobe RGB at 16 bit, I get a readout
> of R=197,G=197,B=192 a tiny bit yellow I admit but I thought I could
> live with that being tired of mixing paint. I have never used a D50
> but I bet they are not much better than that.
> Anyway, next I convert the raw image, to Tiff with RSE and PSD with
> ACR, with no modifications in either converter, and open them with CS2.
> I do this on two computers, my fast one and my slow one. My working
> space is Adobe RGB and mode is 16 bit/channel. Both computers CS2
> environments are identical and both use CRTs.
> After the conversion I have both the Tiff and the PSD loaded on each
> computer. I check the readouts at the several coordinates and get the
> exact same reading on both the output from RSE and ACR - e.g., at
> 5000x3500, I get R=196,G=197,B=191. This is a surprise but also a
> relief. I kinda thought they would convert them slightly differently.
> Then I set CS2 to display the image of the converted raw file, the PSD,
> in full screen preview. So now I have a Photoshop image of my raw file
> displayed on the CRT. Then I set the original raw file still in the
> camera as the source for the custom white balance setting for the
> camera.
> Next I photograph the Photoshop image at a quarter second to get
> several screens of refreshed image.
> Then I load that image back into RSE and ACR. So what do you think I
> get? I thought I would get a nice neutral image possibly a little
> yellow. But no! I get a very blue image. What could be going on? A
> typical reading after the photo is R=56,G=87,B=143. Look how blue that
> is. Can someone help me interpret these results? Shouldn't this be
> a good test for checking the color moving through the system?

Hi Ron,

Not many people have systematically calibrated their system, from start to
finish, as you have, so congratulations. My guess is that your results will
be of interest to others.

Now for your questions. The missing piece of information is monitor
calibration. More than likely you have the color temp of your monitor set
to something like 6500 - a rather blue appearance. Try dropping the color
temp to about 5500 or so, using Adobe Gamma or some other means such as
adjusting using your video driver, and you should get closer to neutral.

As for whether it's a good test for color moving through your system: I
suggest you ignore what others say and continue your experiments to their
logical conclusion. I think you have concocted something original and even
revolutionary that may form the basis for others to calibrate their systems
without expensive equipment. Keep us posted.
--

Mike Russell
www.curvemeister.com/forum/

Bart van der Wolf

2006-08-16, 6:21 am

<ronviers@XXXXXXXXXX> wrote in message
news:1155716764.359019.279410@m73g2000cwd.googlegroups.com...
SNIP
> Can someone help me interpret these results?

It indicates that your display is emitting light with a higher color
temperature than your camera is assuming. Many default to something
like 9500 Kelvin. You could try, if possible with your camera, to
manually set the Whitebalance to something like that, and see how it
looks then.

The kind of neutral (but slightly yellow) backdrop looks that way to
your camera when captured with the lightsource and colorbalance you
used. Your display will emit those colors with its own whitepoint /
color-temperature setting. The eyedropper measurement is just the
signal that gets sent to your display, not what is emitted.

Besides, your camera may respond differently to the display's color
temperature than to your original capture's color temperature. That
has to do with things like metamerism and color (in-)consistency.

--
Bart

ronviers@gmail.com

2006-08-16, 6:21 am

> More than likely you have the color temp of your monitor set
> to something like 6500 - a rather blue appearance. Try dropping the color
> temp to about 5500 or so, using Adobe Gamma or some other means such as
> adjusting using your video driver, and you should get closer to neutral.
>

Mike that was an amazing bit of diagnostics; I had my monitor
temperature set to 6500. I reset it and reshot and got a
R=100,G=101,B=98- just what I was hoping for. Notice it maintained
that bit of yellow all the way through.

Thanks,
Ron

ronviers@gmail.com

2006-08-16, 6:21 am

> It indicates that your display is emitting light with a higher color
> temperature than your camera is assuming. Many default to something
> like 9500 Kelvin.

You are exactly right. It amazes me how well you see the big picture.

Thanks as always,
Ron

ronviers@gmail.com

2006-08-16, 6:16 pm

> Not many people have systematically calibrated their system, from start to
> finish, as you have, so congratulations. My guess is that your results will
> be of interest to others.
>
> Now for your questions. The missing piece of information is monitor
> calibration. More than likely you have the color temp of your monitor set
> to something like 6500 - a rather blue appearance. Try dropping the color
> temp to about 5500 or so, using Adobe Gamma or some other means such as
> adjusting using your video driver, and you should get closer to neutral.
>
> As for whether it's a good test for color moving through your system: I
> suggest you ignore what others say and continue your experiments to their
> logical conclusion. I think you have concocted something original and even
> revolutionary that may form the basis for others to calibrate their systems
> without expensive equipment. Keep us posted.
> --
>

I thought of one more step and it should be the first one. First set
the 'Windows Desktop' to white. Then clear all icons and put the
theme to Windows Classic to get rid of the blue line at the bottom.
This turns the monitor into a white light. Then point the monitor at
the titanium white backdrop and photograph the backdrop using raw.
Then load that image into ACR or RSE to get a balance then adjust the
monitor's temp according to that and reshoot as needed. This should
complete the loop. Does that sound reasonable?

Thanks,
Ron

Kingdom

2006-08-16, 6:16 pm

"ronviers@XXXXXXXXXX" <ronviers@XXXXXXXXXX> wrote in
news:1155722880.872559.28420@75g2000cwc.googlegroups.com:

>
>
> You are exactly right. It amazes me how well you see the big picture.
>
> Thanks as always,
> Ron
>
>

We just enjoyed the round trip on this one.

--
------------------------------------------------------------------------
Learning is not attained by chance, it must be sought for with ardor and
attended to with diligence.
------------------------------------------------------------------------

ronviers@gmail.com

2006-08-16, 10:16 pm

>
> The kind of neutral (but slightly yellow) backdrop looks that way to
> your camera when captured with the lightsource and colorbalance you
> used. Your display will emit those colors with its own whitepoint /
> color-temperature setting. The eyedropper measurement is just the
> signal that gets sent to your display, not what is emitted.
>
> Besides, your camera may respond differently to the display's color
> temperature than to your original capture's color temperature. That
> has to do with things like metamerism and color (in-)consistency.
>

I got some sleep and then reread your reply. Are you saying the test
is bogus?

Thanks,
Ron

ronviers@gmail.com

2006-08-17, 10:17 pm

> The kind of neutral (but slightly yellow) backdrop looks that way to
> your camera when captured with the lightsource and colorbalance you
> used. Your display will emit those colors with its own whitepoint /
> color-temperature setting. The eyedropper measurement is just the
> signal that gets sent to your display, not what is emitted.
>
> Besides, your camera may respond differently to the display's color
> temperature than to your original capture's color temperature. That
> has to do with things like metamerism and color (in-)consistency.
>
> --
> Bart

If I create a jpg image using CS2 with the following options:

No color management
8 bit/Gray scale
Size = 3072x2048
Filled with R=170,G=170,B=170

And saved with the following options:

No ICC profile
Quality maximum
Baseline standard

Then upload the image to my camera (300d) and use the image for the
custom wb source - will this enable me to get more consistent results
from my cameras internal metering and software and enable me to use the
camera for things like mixing paints for correcting color balance and
balancing the RGB guns of my CRT?

Thanks,
Ron

Mike Russell

2006-08-17, 10:17 pm

From: <ronviers@XXXXXXXXXX>
>
> If I create a jpg image using CS2 with the following options:
>
> No color management
> 8 bit/Gray scale
> Size = 3072x2048
> Filled with R=170,G=170,B=170
>
> And saved with the following options:
>
> No ICC profile
> Quality maximum
> Baseline standard
>
> Then upload the image to my camera (300d) and use the image for the
> custom wb source - will this enable me to get more consistent results
> from my cameras internal metering and software and enable me to use the
> camera for things like mixing paints for correcting color balance and
> balancing the RGB guns of my CRT?

Hi Ron,

Possibly, but the details that Bart mentioned will prevent perfect color
reproduction . The reason has to do with the fact that color is the result
of a combination of physical, perceptual, and cognitive processes, none of
which are represented completely in the RGB definition of a color, or the
representation of color on the printed page using cyan, magenta, and yellow
(and other) inks.

In the case of some colors, such as deep blues and purples, this
representation falls flat.

Talk is cheap, and what counts is results. What no one can answer is
whether you are on the track of something new that will help us calibrate
things reasonably well without the use of expensive instruments. This is
why I'd encourage you to complete your experiments and let the rest of us
know how well it works. If, for example, you can get a good neutral gray
this way, that's a big step in the right direction.
---
Mike Russell
www.curvemeister.com/forum/

ronviers@gmail.com

2006-08-17, 10:17 pm

> Hi Ron,
>
> Possibly, but the details that Bart mentioned will prevent perfect color
> reproduction . The reason has to do with the fact that color is the result
> of a combination of physical, perceptual, and cognitive processes, none of
> which are represented completely in the RGB definition of a color, or the
> representation of color on the printed page using cyan, magenta, and yellow
> (and other) inks.
>
> In the case of some colors, such as deep blues and purples, this
> representation falls flat.
>
> Talk is cheap, and what counts is results. What no one can answer is
> whether you are on the track of something new that will help us calibrate
> things reasonably well without the use of expensive instruments. This is
> why I'd encourage you to complete your experiments and let the rest of us
> know how well it works. If, for example, you can get a good neutral gray
> this way, that's a big step in the right direction.
> ---
> Mike Russell
> www.curvemeister.com/forum/

Thanks Mike,
This is a nice project. When I am out of ideas for shooting and tired
of Photoshop tutorials I can occupy myself with understanding my
equipment. Even if the idea ultimately goes nowhere I will not be
disappointed.
It's all about control.

Ron

Peter Wollenberg

2006-08-18, 6:17 am

"ronviers@XXXXXXXXXX" <ronviers@XXXXXXXXXX> wrote:

....
>
>If I create a jpg image using CS2 with the following options:
>
>No color management
>8 bit/Gray scale
>Size = 3072x2048
>Filled with R=170,G=170,B=170
>
>And saved with the following options:
>
>No ICC profile
>Quality maximum
>Baseline standard
>
>Then upload the image to my camera (300d) and use the image for the
>custom wb source - will this enable me to get more consistent results
>from my cameras internal metering and software and enable me to use the
>camera for things like mixing paints for correcting color balance and
>balancing the RGB guns of my CRT?
>
....
If it was that easy ;) I think you did not undestand the concept of
white balancing yet, and, there is no need for white balancing in the
camera if you set up a raw workflow.

I'd recommend you go to the Adope page on CS2 camera raw file support:

http://www.adobe.com/ap/products/ph...ml?camerarawnav

and read the two papers on "Understanding digital raw capture" and
"Linear gamma". If you like Bruce Fraser's writing, consider to buy
his book "Real World Camera Raw with Adobe Photoshop CS2"

URL at amazon:
http://tinyurl.com/ruvnk

The book is rather cheap, but you will also need a Gretag Macbeth
Munsell Color Checker with 24 swatches. Read the book first since
there are several flavors of the Color Checker and you shold buy the
right one.
In the book you will find a detailed description on how to calibrate
the Adobe raw converter for your camera. A link is provided to a
(free) action, which will perform the calibration for you, if you
supply a shot of the color checker taken at reasonable lighting
conditions.

Peter

Andrew Morton

2006-08-18, 6:17 am

ronviers@XXXXXXXXXX wrote:
> If I create a jpg image using CS2 with the following options:
>
> No color management
> 8 bit/Gray scale
> Size = 3072x2048
> Filled with R=170,G=170,B=170

Jpeg compression does not preserve colours; you'll need to check if jpeg
greyscale compression keeps the same values before going any further with
that idea.

Andrew

ronviers@gmail.com

2006-08-18, 6:16 pm

Hi Andrew,
Thanks for the feedback. I realize now that the jpeg will not work. I
am looking into replacing the data in a raw image and copying it back
to the camera.

Ron

ronviers@gmail.com

2006-08-18, 6:16 pm

Peter Wollenberg wrote:
> "ronviers@XXXXXXXXXX" <ronviers@XXXXXXXXXX> wrote:
>
> ...
> ...
> If it was that easy ;) I think you did not undestand the concept of
> white balancing yet, and, there is no need for white balancing in the
> camera if you set up a raw workflow.
>
> I'd recommend you go to the Adope page on CS2 camera raw file support:
>
> http://www.adobe.com/ap/products/ph...ml?camerarawnav
>
> and read the two papers on "Understanding digital raw capture" and
> "Linear gamma". If you like Bruce Fraser's writing, consider to buy
> his book "Real World Camera Raw with Adobe Photoshop CS2"
>
> URL at amazon:
> http://tinyurl.com/ruvnk
>
> The book is rather cheap, but you will also need a Gretag Macbeth
> Munsell Color Checker with 24 swatches. Read the book first since
> there are several flavors of the Color Checker and you shold buy the
> right one.
> In the book you will find a detailed description on how to calibrate
> the Adobe raw converter for your camera. A link is provided to a
> (free) action, which will perform the calibration for you, if you
> supply a shot of the color checker taken at reasonable lighting
> conditions.
>
> Peter

Hi Peter,
I realize the jpeg will not work. But let's say I replace the data in
a raw file with perfectly neutral data then copy that back to the
camera then set that as my custom wb source then shoot jpeg to balance
my colors. Won't that work?

Thanks,
Ron

ronviers@gmail.com

2006-08-18, 6:16 pm

> I'd recommend you go to the Adope page on CS2 camera raw file support:
>
> http://www.adobe.com/ap/products/ph...ml?camerarawnav
>
> and read the two papers on "Understanding digital raw capture" and
> "Linear gamma". If you like Bruce Fraser's writing, consider to buy
> his book "Real World Camera Raw with Adobe Photoshop CS2"
>
> URL at amazon:
> http://tinyurl.com/ruvnk
>
> The book is rather cheap, but you will also need a Gretag Macbeth
> Munsell Color Checker with 24 swatches. Read the book first since
> there are several flavors of the Color Checker and you shold buy the
> right one.
> In the book you will find a detailed description on how to calibrate
> the Adobe raw converter for your camera. A link is provided to a
> (free) action, which will perform the calibration for you, if you
> supply a shot of the color checker taken at reasonable lighting
> conditions.
>
> Peter

I forgot to say that I appreciate the links and other information and
that I have downloaded the pdfs and will read them later today.
Unfortunately buying books and charts are out of the question for now.

Thanks,
Ron

Johan W. Elzenga

2006-08-18, 6:16 pm

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

> I realize the jpeg will not work. But let's say I replace the data in
> a raw file with perfectly neutral data then copy that back to the
> camera then set that as my custom wb source then shoot jpeg to balance
> my colors. Won't that work?

I'm not sure what exactly you want to achieve, but a better white
balance is not what you will achieve if that's your aim. The principle
of 'custom' white balancing is that you shoot a neutral grey card in a
certain light, so you can compensate for the color cast that this light
source would cause by comparing this shot against neutral grey.
Consequently, the reference shot is normally *NOT* neutral grey, that is
exactly why you use it for white balancing in the first place. Replacing
the reference shot by an artificially made neutral shot will make white
balancing go wrong, not be more accurate. Also, your camera does not use
this reference shot for anything other than to set the white balance to
the light source in question. It is not 'calibrated' against this shot,
nor will it calibrate itself against that shot.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-18, 6:16 pm

> I'm not sure what exactly you want to achieve, but a better white
> balance is not what you will achieve if that's your aim. The principle
> of 'custom' white balancing is that you shoot a neutral grey card in a
> certain light, so you can compensate for the color cast that this light
> source would cause by comparing this shot against neutral grey.
> Consequently, the reference shot is normally *NOT* neutral grey, that is
> exactly why you use it for white balancing in the first place. Replacing
> the reference shot by an artificially made neutral shot will make white
> balancing go wrong, not be more accurate. Also, your camera does not use
> this reference shot for anything other than to set the white balance to
> the light source in question. It is not 'calibrated' against this shot,
> nor will it calibrate itself against that shot.
>
>
> --
Hi Johan,
I am not going for accuracy just consistancy.

Thanks,
Ron

Johan W. Elzenga

2006-08-18, 6:16 pm

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

> Hi Johan,
> I am not going for accuracy just consistancy.

But why would this give more consistant results than just setting the
white balance at a fixed value, say 5500 K? That is exactly what you
would be doing with this method, except you'd be using a very
complicated way of achieving that result.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-18, 6:16 pm

> But why would this give more consistant results than just setting the
> white balance at a fixed value, say 5500 K?

It may not but I want out of the auto modes in hopes of minimizing the
magic the Canon OS performs.

Thanks,
Ron

Johan W. Elzenga

2006-08-18, 6:16 pm

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

>
> It may not but I want out of the auto modes in hopes of minimizing the
> magic the Canon OS performs.

Doesn't the 300D have a fixed white balance setting? It should have
many, because 'Sunny' or 'Cloudy' or something like that are all fixed
white balance settings, not automatic settings that change with the
situation.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-18, 6:16 pm

>
> Doesn't the 300D have a fixed white balance setting? It should have
> many, because 'Sunny' or 'Cloudy' or something like that are all fixed
> white balance settings, not automatic settings that change with the
> situation.
>

Hi Johan,

I think you are right. I have been looking at the parameters passed to
and from the camera here:
http://www.sno.phy.queensu.ca/~phil...#CameraSettings

They look a little unwieldy at first but in fact not many apply to the
300d and very few are relevant in manual mode and even fewer with no in
camera processing. There seems to be less magic than I assumed - even
with the 1D Mark II.
I am going to try again when things get dark, just as you suggest, with
one of the predefined color balance selections.

Thanks,
Ron

Johan W. Elzenga

2006-08-18, 10:16 pm

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

>
> Hi Johan,
>
> I think you are right. I have been looking at the parameters passed to
> and from the camera here:
>http://www.sno.phy.queensu.ca/~phil...non.html#Camera
>Settings
>
> They look a little unwieldy at first but in fact not many apply to the
> 300d and very few are relevant in manual mode and even fewer with no in
> camera processing. There seems to be less magic than I assumed - even
> with the 1D Mark II.

That's correct. There's very little magic with white balancing. As the
name suggests, 'auto' is a setting that changes with the situation. The
camera tries to get the best white balance, based upon the readings of
the metering system. But all the other settings are fixed settings.

Also note that if you are shooting in RAW, the white balance is set
during RAW conversion, not during shooting. You can set it to anything
you like in the RAW converter, so that makes it simple to have all your
sohts with the same white balance. The camera setting is used as the
default setting for the RAW converter, but apart from that it has no
influence on the RAW file whatsoever.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-18, 10:16 pm

I have:
Daylight
Shade
Cloudy
Tungsten
Fluorescent
Flash

I am guessing 'Flahs' is the most neutral. I think I will start with
that. Surely it is not bluer than 'Fluorescent'.

Johan W. Elzenga

2006-08-18, 10:16 pm

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

> I have:
> Daylight
> Shade
> Cloudy
> Tungsten
> Fluorescent
> Flash
>
> I am guessing 'Flahs' is the most neutral. I think I will start with
> that. Surely it is not bluer than 'Fluorescent'.

'Flash' is 6650 K for my 1Ds MkII, so it's probably the same for your
camera. You still seem to have a problem understanding white balancing,
however.

There is no such thing as a 'neutral' white balance, and 'flash' is no
more or no less neutral then 'daylight', 'cloudy' or 'shade'. The white
balance setting must match the color temperature of the light, only then
the result is neutral. That means that a 'neutral' white balance is
depending on the light source. 'Daylight' is around 5250 K, so that is
neutral if the light is really 5250 K. Use it indoors with tungsten
lights and it's suddenly far too warm (too orange/yellow). Use it on a
cloudy day or in the shadow, and the result is too cold (too blue).
'Cloudy' is 6100 K, 'Shade' is 7100 K, so 'Flash' is somewhere in
between these two.

Fluorescent is a tricky one, because it is meant to correct the
non-continuous fluorescent light spectrum. The color temperature is only
4100 K, but with a strong extra magenta correction because fluorescent
light is greenish.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-18, 10:16 pm

Ok, this is what I want:
I want to photograph a neutral backdrop in neutral light and view the
subject in CS2 in Adobe RGB space with my custom monitor profile using
my CRT. All I need to do this is to have single thing anywhere in the
chain that I can trust. This is why I wanted an image in the camera
with no color balancing. So I am back to modifying a raw and uploading
it to the camera and setting it as the source for custom wb and
reshooting in jpeg and rebalancing my lights and feeding the image back
through the system.
You are probably right about my having a misunderstanding about wb - I
can be very thick headed.

Thanks,
Ron

Johan W. Elzenga

2006-08-19, 6:16 am

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

> Ok, this is what I want:
> I want to photograph a neutral backdrop in neutral light and view the
> subject in CS2 in Adobe RGB space with my custom monitor profile using
> my CRT. All I need to do this is to have single thing anywhere in the
> chain that I can trust.

What is 'neutral light'? As I tried to explain, 'neutral light' does not
exist. The combination of the color temperature of the light and the
white balance setting makes the result neutral. That's why this is
called white 'balance'. You balance the temperature setting with the
actual temperature of the light, in order to get them the same.

You do have the item you can trust: the grey card. Shoot that grey card
in RAW, use the grey eyedropper when you set the white balance in the
RAW converter and you'll have a photograph of a perfectly neutral grey
card. That's the way all professionals solve this problem. Use this
white balance setting on all the other shots in the same session and
you'll have perfectly neutral photos. Yes, it's that easy.

> So I am back to modifying a raw and uploading
> it to the camera and setting it as the source for custom wb and
> reshooting in jpeg and rebalancing my lights and feeding the image back
> through the system.
> You are probably right about my having a misunderstanding about wb - I
> can be very thick headed.

With all respect; you sound like somebody who tries to fly by lifting
himself up. People tell you that will never work, but you continue to
try saying "I may not understand gravity, but I can be very thick
headed". Yes, apparently. But that still won't make you fly.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

Mike Russell

2006-08-19, 10:16 pm

"Johan W. Elzenga" <nomail@please.invalid> wrote in message
news:1hkbeaq.18jstfkezqk1wN%nomail@please.invalid...
> ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:
>
>
> What is 'neutral light'? As I tried to explain, 'neutral light' does not
> exist.

If colored light exists, then so does neutral light. Neutral light is light
without color.

> The combination of the color temperature of the light and the
> white balance setting makes the result neutral. That's why this is
> called white 'balance'. You balance the temperature setting with the
> actual temperature of the light, in order to get them the same.

Another way is to use an object with a known neutral color as a reference.
Other reference colors may be used, for example a skin tone, foliage, or
other recognizeable color that is important to the content of the image.

> You do have the item you can trust: the grey card. Shoot that grey card
> in RAW, use the grey eyedropper when you set the white balance in the
> RAW converter and you'll have a photograph of a perfectly neutral grey
> card. That's the way all professionals solve this problem. Use this
> white balance setting on all the other shots in the same session and
> you'll have perfectly neutral photos. Yes, it's that easy.

Most photographs contain mixed lighting effects due to multiple light
sources, such as sky and sun, and shadows colored by reflected light from
other objects in the scene. The final color correction should attempt to
neutralize all of these effects, or make a compromise between then.

<snip>
--

Mike Russell
www.curvemeister.com/forum/

ronviers@gmail.com

2006-08-19, 10:16 pm

>
> With all respect; you sound like somebody who tries to fly by lifting
> himself up. People tell you that will never work, but you continue to
> try saying "I may not understand gravity, but I can be very thick
> headed". Yes, apparently. But that still won't make you fly.
>
>
> --
>
Johan please do not get aggravated with me; I cannot help how I am. I
mentioned earlier in the thread that it does not need to come to
something.

I realized that all I need to do to get neutral data into the camera is
to either fully saturate the sensor or completely deplete it. So I
first took a picture at 1/4000 of a second with aperture closed and
lens cap on at ISO 100. I know that all sounds redundant but I tried
other settings with the lens cap on and those settings gave me the
skinniest (most dark) histogram. Then I took another picture while
holding the camera directly at a light with a 30 sec exposure. All the
histogram flashed so I knew it was full. Then I used the black (fully
depleted) image as the source file for wb. Then I took a picture of a
backdrop with a blue cast. This gave me an image of R=76,G=117,B=58.
Then I took the same picture with the white (fully saturated) image as
the source for wb and got R=77,G=117,B=59. Consistency! Now all I have
to do is create an image in CS2 with the color ratio of something like
R=131,G=100,B=159 to cancel out the green then I should have a truly
white subject to photograph so I can remix my paints and get rid of the
blue cast on the original backdrop. So my question is, can anyone
explain why, if I use either the depleted or saturated image as a
source for wb the resulting image is so green? And remember it is
green even though I am photographing a subject that has a blue cast.
Btw, green does not bother me as long I can count on those ratios.

Thanks,
Ron

Johan W. Elzenga

2006-08-19, 10:16 pm

Mike Russell <RE-MOVEmike@Curvemeister.comRE-MOVE> wrote:

> "Johan W. Elzenga" <nomail@please.invalid> wrote in message
> news:1hkbeaq.18jstfkezqk1wN%nomail@please.invalid...
>
> If colored light exists, then so does neutral light. Neutral light is light
> without color.

Correct. But 'without color' doesn't mean 'without color temperature'
and that is what white balancing is all about.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

Johan W. Elzenga

2006-08-19, 10:16 pm

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

> Johan please do not get aggravated with me; I cannot help how I am. I
> mentioned earlier in the thread that it does not need to come to
> something.
>
> I realized that all I need to do to get neutral data into the camera is
> to either fully saturate the sensor or completely deplete it. So I
> first took a picture at 1/4000 of a second with aperture closed and
> lens cap on at ISO 100. I know that all sounds redundant but I tried
> other settings with the lens cap on and those settings gave me the
> skinniest (most dark) histogram. Then I took another picture while
> holding the camera directly at a light with a 30 sec exposure. All the
> histogram flashed so I knew it was full. Then I used the black (fully
> depleted) image as the source file for wb. Then I took a picture of a
> backdrop with a blue cast. This gave me an image of R=76,G=117,B=58.
> Then I took the same picture with the white (fully saturated) image as
> the source for wb and got R=77,G=117,B=59. Consistency! Now all I have
> to do is create an image in CS2 with the color ratio of something like
> R=131,G=100,B=159 to cancel out the green then I should have a truly
> white subject to photograph so I can remix my paints and get rid of the
> blue cast on the original backdrop. So my question is, can anyone
> explain why, if I use either the depleted or saturated image as a
> source for wb the resulting image is so green? And remember it is
> green even though I am photographing a subject that has a blue cast.
> Btw, green does not bother me as long I can count on those ratios.

I give up. I've tried to explain to you what a custom white balance
does, but I failed.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

Notneural@att.net

2006-08-19, 10:16 pm

Mike Russell wrote:

> Most photographs contain mixed lighting effects due to multiple light
> sources, such as sky and sun, and shadows colored by reflected light from
> other objects in the scene.

You are absolutely correct about multiple light sources in an image. In
fact, unless an image is captured in a controlled lighting condition,
like in a studio, the vast majority of images taken either indoor or
outdoor will be lit by multiple light sources. This is taking into
consideration of reflected light from e.g. walls, foliage, etc. even if
the main light source is "neutral".

> The final color correction should attempt to
> neutralize all of these effects, or make a compromise between then.

This is the part I respectfully disagree. In many images, such as a
sunrise/sunset landscape, or an indoor portrait lit by candle light,
neutralizing the multiple light sources will defeat the intent or mood.
These images are often the most striking but unfortunately are the most
difficult to color correct. The common practice to set (true) black and
white points and neutralize a known neutral won't work here, because
there aren't any. It calls for subjective interpretation and much more
intricate rgb tweaking than getting a r=g=b neutral. Including a gray
card in such images for reference also makes no sense and serves no
purpose. I wish there are more tutorials on this topic.

ronviers@gmail.com

2006-08-19, 10:16 pm

Johan W. Elzenga wrote:
> ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:
>
>
> I give up. I've tried to explain to you what a custom white balance
> does, but I failed.
>
>
> --
> Johan W. Elzenga johan<<at>>johanfoto.nl
> Editor / Photographer http://www.johanfoto.nl

One of the first tests I did with my camera was to photograph a
backdrop lighted at the top with tungsten and at the bottom with
fluorescent. Then used that image as a source for custom wb then shot
the image again. I learned that, at least with my camera, there is not
a pixel by pixel neutralization of white. I could get one of the
whites neutral but not both. It was not all bad though because after
balancing one color it left me with a gradient that I could use in PS
to balance the other white.

Brgds,
Ron

ronviers@gmail.com

2006-08-19, 10:16 pm

Guess which raw image was bigger the one with depleted sensor or
saturated sensor?

Mike Russell

2006-08-19, 10:16 pm

<Notneural@att.net> wrote in message news:44E72CA0.DBAA6EDD@att.net...
> Mike Russell wrote:
>
>
> This is the part I respectfully disagree. In many images, such as a
> sunrise/sunset landscape, or an indoor portrait lit by candle light,
> neutralizing the multiple light sources will defeat the intent or mood.

You are correct, of course, about sunsets and the like. These are special
cases where the effect of colored light is important. The light itself
forms part of the subject of the picture, if you will. Neutralizing the
color of such light would result in a less interesting image. But this does
not negate the usefulness of setting a neutral for 90 percent of our images.

For the majority of images, there is no significance to the color cast,
other than the undesirable effect of veiling the colors of the objects in
the image. The concept using a neutral or a reference color to remove color
casts is a basic part of color correction. Correction in this case is based
on the numbers; because of visual effects such as adaptation and
simultaneous contrast, the appearance on screen is generally deceptive.

> These images are often the most striking but unfortunately are the most
> difficult to color correct.

Difficult in a way, because with highly colored light there is no set
reference to correct to. But they can be easier, in a way, to color correct
because there is less need to fuss about neutrals, skin tones, and the like,
and more freedom to play with saturation and hue. For images like this, I
find myself relying more on what the image looks like on screen.

> The common practice to set (true) black and
> white points and neutralize a known neutral won't work here, because
> there aren't any. It calls for subjective interpretation and much more
> intricate rgb tweaking than getting a r=g=b neutral. Including a gray
> card in such images for reference also makes no sense and serves no
> purpose.

A gray card can be of some use in these situations, if it is oriented in a
non-intuitive way. For example, for a sunset, the gray card should be
illuminated by the colored light, and a reference image taken with the
camera facing away from the sunset.

> I wish there are more tutorials on this topic.

If you haven't read Dan Margulis yet, there is a wealth of information and
technique in his books. What endears his work to me is that his concepts
are always illustrated with specific images. Other authors simply wave
their hand in the air to get the concept across, and skip the (more
difficult) task of providing a specific example in the form of a real
photograph that benefits from the technique.
--
Mike Russell
www.curvemeister.com/forum/

KSL

2006-08-20, 6:17 am

Ron,

I have been following this thread closely and, while I definitely am no
expert, I think I see where you are having difficulty with the concept of
colour balancing.

Firstly, when taking the photo to produce your reference image, *you*
determine what *you* decree to be a neutral shade. For some people a piece
of white office paper is their chosen object. For others, they may prefer
to use something far more standardised such as a Kodak Grey card as it will
ensure consistency.

The Grey Card is produced to fit in with a man-made definition of 'neutral'.

Now, let's assume you illuminate this grey card with light that is rich in
blue. The light reflected off the card will now be rich in blue. But you
want it to be same as the card, so you need to remove an equal amount of
blue when producing the final image.

To tell the camera how much blue to remove, you take a photo of *your*
'neutral' object under the exact lighting conditions the photo fo your
definitve subject is to be taken. The camera then can work out in what way
the colour of the reference image differs from "neutral".

What you camera does when you set the custom white balance is it reads the
colour of the reference image, which is a representation of the colour of
the light reflected off your reference object (the Grey Card) and it
determines in what way the values differ from those of the classic
definition of neutral (R=G=B). Once it knows the differential it can then
use that information to adjust all subsequent photos taken with *that*
particular custom white balance setting.

If you change the lighting conditions the light reflected off the grey card
will be different, you will need to generate a new reference image and the
camera will then adjust the subsequent photos using the new values.

When you select one of the pre-programmed settings such as daylight,
incandescent, flash, etc. all the camera is doing is using built-in values
to make the adjustments. It is as if it is reading some built-in reference
images of a grey-card. In other words, if you set it to 'daylight', the
camera uses some pre-determined values that would equate to the values it
would have used had you shot a reference image of a Grey Card under
'daylight' light.

The problem with the pre-set options is that they are just good guesses.
The daylight at dawn is quite a different colour from that at midday which
is in turn quite different from that at dusk. They are all 'daylight' but
are all different colour temperatures.

Of course, if you want your white car to look like it was taken at sunset
and you are taking your photo at sunset then the image will be as you
desire. The car will be redder, but your eye and brain will still be able
to work out that it is white, using the overall image for reference. But
if you want your white car to actually be the same colour in the photos you
take of it at midday and later in the afternoon, you will have to use custom
white balance settings for both the midday and the evening photos.

I hope this rather long-winded explanation helps.

I also invite all comments about what I have said - that's how I learn. :-)

Ken

<ronviers@XXXXXXXXXX> wrote in message
news:1156009916.294755.165780@m79g2000cwm.googlegroups.com...

> One of the first tests I did with my camera was to photograph a
> backdrop lighted at the top with tungsten and at the bottom with
> fluorescent. Then used that image as a source for custom wb then shot
> the image again. I learned that, at least with my camera, there is not
> a pixel by pixel neutralization of white. I could get one of the
> whites neutral but not both. It was not all bad though because after
> balancing one color it left me with a gradient that I could use in PS
> to balance the other white.
>
> Brgds,
> Ron
>

ronviers@gmail.com

2006-08-20, 6:15 pm

Hi Ken,
Thanks for the explanation. All I was trying to do was stick white in
one end of my system and verify that I get white out of the other. To
do this I was trying to use the sensors and meters built in to my
camera. What I need for you or someone to do is explain, in a way that
I can understand, why it cannot be done. Otherwise it is something I
would like to pursue in my spare time. I think I have made progress by
getting neutral reference images but I have spent the day taking kitten
pictures so I am really stressed out and want to come back to it in a
few days. Everyone keeps writing about white balance so today I wake
up dreaming about colored spider webs coming out of sheep teats. All I
could think of was that spider webs should be neutral.

Thanks,
Ron

KSL

2006-08-20, 6:16 pm

Ron,

The first problem I see is ... how do you define white?

But that is not so important. What I think you are really trying to do is
ascertain that if you input light of a particular colour into your system
you want to get the exact same colour out of the system.

Presumably, white is not the main concern. Presumably, you want that if you
photograph a red ball or green leaf the ball must look the same shade of red
and the leaf must look the same shade of green when viewed on the monitor as
they looked in 'real life'?

I think I have explained why it is not that easy to specify the colour of
the light going into the system, but I don't think it really matters.

Now we need to look at the output end. Here is a big problem. Just as the
colour of the light entering the system through the lens to hit the sensor
is dependent on the colour of the light hitting the subject and the colour
of the subject itself, the colour of the light exiting the system is
dependent on your monitor.

Ron, presumably, you have been to a large store that sells TVs. There are
dozens of TVs on the walls, all showing the same images. You will be hard
pressed to find two of those TVs that look identical. They have the
identical signal coming in, but put different colour images out.

In the exact same way as the TVs all differ, all monitors differ. There are
ways to calibrate monitors to a set standard. The results will vary
according the quality of the calibration equipment used (and the skill of
the operator) but one can get pretty close to a uniform output across
monitors.

Take the file of the image you have generated and do your 'photographing the
monitor' routine using a few different monitors. You will get different
output on each of the monitors unless they have all been calibrated
extremely well.

Even if you have your monitor calibrated to an excellent standard, the
images will appear different depending on the ambient light in the room in
which you are viewing the monitor.

You put a lot of effort into calibrating the input side (Titanium paint,
special lights,etc.) to get as close to your definition of pure (neutral)
white as possible. You now need to put an equal effort into calibrating the
output side to the same standard.

Then, if you want printed output, you need to calibrate your printer to the
same standard.

Ron, you need to be realistic about this. Even with film, different batches
of the same brand and type of film vary. That is why professional
photographers ensure that when they buy film for a project all the rolls
have the same emulsion batch number. The paint industry has similar
problems. The printing industry likewise. You just have to accept that
*PERFECT* colour reproduction is a holy grail that is not attainable.

Sure, aim high, but there is no point in trying to achieve the impossible.

Ken

<ronviers@XXXXXXXXXX> wrote in message
news:1156073861.854185.281070@m79g2000cwm.googlegroups.com...
>
> Hi Ken,
> Thanks for the explanation. All I was trying to do was stick white in
> one end of my system and verify that I get white out of the other. To
> do this I was trying to use the sensors and meters built in to my
> camera. What I need for you or someone to do is explain, in a way that
> I can understand, why it cannot be done. Otherwise it is something I
> would like to pursue in my spare time. I think I have made progress by
> getting neutral reference images but I have spent the day taking kitten
> pictures so I am really stressed out and want to come back to it in a
> few days. Everyone keeps writing about white balance so today I wake
> up dreaming about colored spider webs coming out of sheep teats. All I
> could think of was that spider webs should be neutral.
>
> Thanks,
> Ron
>

Bart van der Wolf

2006-08-20, 6:16 pm

"Mike Russell" <RE-MOVEmike@Curvemeister.comRE-MOVE> wrote in message
news:_oCFg.10744$kO3.6815@newssvr12.news.prodigy.com...
SNIP
> If colored light exists, then so does neutral light. Neutral light
> is light without color.

Well, it's more like a 'specific' mix of all spectral colors.

And then there is the selective absorption/transmission/reflection by
objects which determines it's color. If the illuminated object
absorbs/transmits/reflects all parts of the spectrum (the visible part
interests most of us here) equally, it's said to have a neutral
appearance, or without a dominant color. It then also is a good proxy
for the overall illumination at that position of the scene.

SNIP
> Another way is to use an object with a known neutral color as a
> reference.

Yes, although if one strives for a very high level of accuracy, things
become a bit tricky again. The problem is that many so-called White
Balancing tools, do not necessarily exhibit a uniform spectral
reflection under different lightsources.

SNIP
> Most photographs contain mixed lighting effects due to multiple
> light sources, such as sky and sun, and shadows colored by reflected
> light from other objects in the scene. The final color correction
> should attempt to neutralize all of these effects, or make a
> compromise between then.

A reflector like a graycard can be used as an integrator of all
incident light. Again, the problem is that most graycards are tools to
determine exposure. They are not certified for a spectrally neutral
reflection. Some may come close when unused, but with use they will
shift due to handling (dirt/wear/bleaching).

Two days ago I measured a couple of common test objects I have.
Amongst them a brand new (never been out of its envelope before) Kodak
Graycard, a Q13 'Grayscale' , and a relatively new BabelColor White
target.

Using an EyeOne Pro spectrophotometer, the Graycard *happened* to be
reasonably Gray, Lab: L=48.6 , a=0.4 , b=-0.9 depending a bit on where
on the card was measured (deltaE=0.4). If we use that to extrapolate
to a White point we'd get something like sRGB: 251, 251, 255 .

The used Q13 'grayscale' reading of the 'M' step (after conversion)
was sRGB=112,117,119 , and that is *supposed* to be shade of gray. The
Q13 'A' step reads sRGB=243,242,238 . Maybe it was better when it was
still new?

The BabelColor White target
(http://www.babelcolor.com/main_level/White_Target.htm) does have a
published manufacturing aim for high neutrality.
My copy measured L=99.7, a=-0.2, b=-0.4, or close to sRGB
253,254,255.

The interesting thing about that target is, that it also is excellent
for determining the maximum non-clipping exposure, very useful for
digicams. It is practically impossible to have a higher (non-specular)
reflection than from that target. It is also extremely neutral
thoughout the visible spectrum and behaves almost identical under
various illuminants. It therefore is an exellent 'reflection' (pun
intended) of the ambient illumination's color 'temperature', or
spectral composition.

--
Bart

ronviers@gmail.com

2006-08-20, 6:16 pm

>
> But that is not so important. What I think you are really trying to do is
> ascertain that if you input light of a particular colour into your system
> you want to get the exact same colour out of the system.
>
> Presumably, white is not the main concern. Presumably, you want that if you
> photograph a red ball or green leaf the ball must look the same shade of red
> and the leaf must look the same shade of green when viewed on the monitor as
> they looked in 'real life'?

Well said.

>
> Ron, presumably, you have been to a large store that sells TVs. There are
> dozens of TVs on the walls, all showing the same images. You will be hard
> pressed to find two of those TVs that look identical. They have the
> identical signal coming in, but put different colour images out.
>

You should have seen the TV walls thirty years ago. Just last week I
was at Wal~mart looking at their TV wall and it was not too bad. The
one thing that caught my eye was that one set was about a half a second
behind the others now that is strange. But back on task; my low end,
five year old 'Gateway EV500' CRTs are pretty darn good. Not
great, I'm not delusional, but I think they are capable of holding a
setup for months at a time.

> In the exact same way as the TVs all differ, all monitors differ. There are
> ways to calibrate monitors to a set standard. The results will vary
> according the quality of the calibration equipment used (and the skill of
> the operator) but one can get pretty close to a uniform output across
> monitors.
>
> Take the file of the image you have generated and do your 'photographing the
> monitor' routine using a few different monitors. You will get different
> output on each of the monitors unless they have all been calibrated
> extremely well.

I disagree, I admit do not know, but I think even two very different
CRTs like a Sony Trinitron and a Phillips using whatever non-Trinitron
gun setup they use, could be set to reproduce color within 1 or 2
percent of each other - and maintain that setup for a half a year or
so.

> Even if you have your monitor calibrated to an excellent standard, the
> images will appear different depending on the ambient light in the room in
> which you are viewing the monitor.

I control for ambient by waiting until dark and turning everything off
and taping over the indicator LEDs.

> You put a lot of effort into calibrating the input side (Titanium paint,
> special lights,etc.) to get as close to your definition of pure (neutral)
> white as possible. You now need to put an equal effort into calibrating the
> output side to the same standard.
>
> Then, if you want printed output, you need to calibrate your printer to the
> same standard.

I don't even want to think about printing yet.

> Ron, you need to be realistic about this. Even with film, different batches
> of the same brand and type of film vary. That is why professional
> photographers ensure that when they buy film for a project all the rolls
> have the same emulsion batch number. The paint industry has similar
> problems. The printing industry likewise. You just have to accept that
> *PERFECT* colour reproduction is a holy grail that is not attainable.
>
> Sure, aim high, but there is no point in trying to achieve the impossible.
>

Ok but you should have seen how far out of whack my equipment was
before I started this project.

Thanks for the suggestions - all good points,
Ron

2006-08-20, 10:16 pm

Ron,

I think we actually are in agreement on this point.

*If* the monitors are very well calibrated, then they will reproduce the
colours quite similarly. The point is that if you are trying your
experiment on an uncalibrated monitor then the results will be incorrect.

Of course, you could use your idea as a way of calibrating your monitor. If
you adjust the monitor so that the results are as you expect them i.e. the
output from the monitor matches the colour mix of the reference image, then
you have basically calibrated the monitor.

It is, of course, vital to this exercise that you don't have the camera
making any adjustments to the colour - you have to shoot in RAW.

Ken

<ronviers@XXXXXXXXXX> wrote in message
news:1156109958.788181.210870@i42g2000cwa.googlegroups.com...
>
> I disagree, I admit do not know, but I think even two very different
> CRTs like a Sony Trinitron and a Phillips using whatever non-Trinitron
> gun setup they use, could be set to reproduce color within 1 or 2
> percent of each other - and maintain that setup for a half a year or
> so.
> Ron
>

Notneural@att.net

2006-08-21, 6:17 pm

There is no question that if a neutral color exists in an image,
neutralizing it is an important part of color correction. So is setting
black/white points if true black/white points exist. Most books and
tutorials recommend these methods. But if no neutral or true black/white
exist in the image, these methods will send you down a wrong and
treacherous path.

If you meant that "90 percent of our images" have neutrals, I would
strongly disagree. That will imply that 90 percent of our images are lit
by a neutral light source, which is simply not true unless they are all
taken in a studio. In fact, I would say 90 percent of our images DON't
have true neutrals. Well, at least mine don't. Yet most books and
tutorials (99.9999 percent) fail to point this out, with the exception
of Margulis' book. The one chapter on deciding what is neutral or not is
worth the price of the book.

But knowing the problem is just the starting point, but how to deal with
it is far more difficult than neutralizing a color. Margulis' book
offers some examples and solutions, but I find many very difficult to
digest or to follow. He is excellent in pointing out the problems, but
tend to wave his hand when it comes to Photoshop details.

Mike Russell wrote:
>
> <Notneural@att.net> wrote in message news:44E72CA0.DBAA6EDD@att.net...
>
> You are correct, of course, about sunsets and the like. These are special
> cases where the effect of colored light is important. The light itself
> forms part of the subject of the picture, if you will. Neutralizing the
> color of such light would result in a less interesting image. But this does
> not negate the usefulness of setting a neutral for 90 percent of our images.
>
> For the majority of images, there is no significance to the color cast,
> other than the undesirable effect of veiling the colors of the objects in
> the image. The concept using a neutral or a reference color to remove color
> casts is a basic part of color correction. Correction in this case is based
> on the numbers; because of visual effects such as adaptation and
> simultaneous contrast, the appearance on screen is generally deceptive.
>
>
> Difficult in a way, because with highly colored light there is no set
> reference to correct to. But they can be easier, in a way, to color correct
> because there is less need to fuss about neutrals, skin tones, and the like,
> and more freedom to play with saturation and hue. For images like this, I
> find myself relying more on what the image looks like on screen.
>
>
> A gray card can be of some use in these situations, if it is oriented in a
> non-intuitive way. For example, for a sunset, the gray card should be
> illuminated by the colored light, and a reference image taken with the
> camera facing away from the sunset.
>
>
> If you haven't read Dan Margulis yet, there is a wealth of information and
> technique in his books. What endears his work to me is that his concepts
> are always illustrated with specific images. Other authors simply wave
> their hand in the air to get the concept across, and skip the (more
> difficult) task of providing a specific example in the form of a real
> photograph that benefits from the technique.
> --
> Mike Russell
> www.curvemeister.com/forum/

KatWoman

2006-08-22, 10:16 pm

<ronviers@XXXXXXXXXX> wrote in message
news:1155986873.469571.212310@i3g2000cwc.googlegroups.com...
>
> Johan please do not get aggravated with me; I cannot help how I am. I
> mentioned earlier in the thread that it does not need to come to
> something.
>
> I realized that all I need to do to get neutral data into the camera is
> to either fully saturate the sensor or completely deplete it. So I
> first took a picture at 1/4000 of a second with aperture closed and
> lens cap on at ISO 100. I know that all sounds redundant but I tried
> other settings with the lens cap on and those settings gave me the
> skinniest (most dark) histogram. Then I took another picture while
> holding the camera directly at a light with a 30 sec exposure. All the
> histogram flashed so I knew it was full. Then I used the black (fully
> depleted) image as the source file for wb. Then I took a picture of a
> backdrop with a blue cast. This gave me an image of R=76,G=117,B=58.
> Then I took the same picture with the white (fully saturated) image as
> the source for wb and got R=77,G=117,B=59. Consistency! Now all I have
> to do is create an image in CS2 with the color ratio of something like
> R=131,G=100,B=159 to cancel out the green then I should have a truly
> white subject to photograph so I can remix my paints and get rid of the
> blue cast on the original backdrop. So my question is, can anyone
> explain why, if I use either the depleted or saturated image as a
> source for wb the resulting image is so green? And remember it is
> green even though I am photographing a subject that has a blue cast.
> Btw, green does not bother me as long I can count on those ratios.
>
> Thanks,
> Ron

after reading all that
please tell me what is the point of this experiment?

what the hell are you trying to take pictures of that needs so much color
fixin' and exactness?

you can mess around all day with your monitor color and then every paper
you print on will have a different white

every lab or bureau will need to shift the profile to match theirs

and every person on the net has a different monitor setting and your photos
will look different

KatWoman

2006-08-22, 10:16 pm

"KSL" <yellow@lipworth dot com.au> wrote in message
news:44e832df$0$5109$afc38c87@news.optusnet.com.au...[color=darkred]
> Ron,
>
> I have been following this thread closely and, while I definitely am no
> expert, I think I see where you are having difficulty with the concept of
> colour balancing.
>
> Firstly, when taking the photo to produce your reference image, *you*
> determine what *you* decree to be a neutral shade. For some people a
> piece of white office paper is their chosen object. For others, they may
> prefer to use something far more standardised such as a Kodak Grey card as
> it will ensure consistency.
>
> The Grey Card is produced to fit in with a man-made definition of
> 'neutral'.
>
> Now, let's assume you illuminate this grey card with light that is rich in
> blue. The light reflected off the card will now be rich in blue. But you
> want it to be same as the card, so you need to remove an equal amount of
> blue when producing the final image.
>
> To tell the camera how much blue to remove, you take a photo of *your*
> 'neutral' object under the exact lighting conditions the photo fo your
> definitve subject is to be taken. The camera then can work out in what
> way the colour of the reference image differs from "neutral".
>
> What you camera does when you set the custom white balance is it reads the
> colour of the reference image, which is a representation of the colour of
> the light reflected off your reference object (the Grey Card) and it
> determines in what way the values differ from those of the classic
> definition of neutral (R=G=B). Once it knows the differential it can then
> use that information to adjust all subsequent photos taken with *that*
> particular custom white balance setting.
>
> If you change the lighting conditions the light reflected off the grey
> card will be different, you will need to generate a new reference image
> and the camera will then adjust the subsequent photos using the new
> values.
>
> When you select one of the pre-programmed settings such as daylight,
> incandescent, flash, etc. all the camera is doing is using built-in values
> to make the adjustments. It is as if it is reading some built-in
> reference images of a grey-card. In other words, if you set it to
> 'daylight', the camera uses some pre-determined values that would equate
> to the values it would have used had you shot a reference image of a Grey
> Card under 'daylight' light.
>
> The problem with the pre-set options is that they are just good guesses.
> The daylight at dawn is quite a different colour from that at midday which
> is in turn quite different from that at dusk. They are all 'daylight' but
> are all different colour temperatures.
>
> Of course, if you want your white car to look like it was taken at sunset
> and you are taking your photo at sunset then the image will be as you
> desire. The car will be redder, but your eye and brain will still be
> able to work out that it is white, using the overall image for reference.
> But if you want your white car to actually be the same colour in the
> photos you take of it at midday and later in the afternoon, you will have
> to use custom white balance settings for both the midday and the evening
> photos.
>
>
> I hope this rather long-winded explanation helps.
>
> I also invite all comments about what I have said - that's how I learn.
> :-)
>
> Ken
>
>
>
>
> <ronviers@XXXXXXXXXX> wrote in message
> news:1156009916.294755.165780@m79g2000cwm.googlegroups.com...
>
TRY a LIGHT or FLASH METER
a measure device to tell you what temp the light is

ronviers@gmail.com

2006-08-23, 3:16 am

[color=darkred]
> please tell me what is the point of this experiment?
>
> what the hell are you trying to take pictures of that needs so much color
> fixin' and exactness?
>
> you can mess around all day with your monitor color and then every paper
> you print on will have a different white
>
> every lab or bureau will need to shift the profile to match theirs
>
> and every person on the net has a different monitor setting and your photos
> will look different

About twenty years ago I found that with the correct sequence of button
presses I could get the computer to dispense a pellet of food. In
order to learn that sequence I had to live and breathe computers. Once
I learned the sequence I was able to live, breathe and eat computers.
Then I got sick and my career came to an end. As I began to recover I
had to take stock and make choices - hence photography.
Sometimes I run out of ideas for shooting, other times my enthusiasm
for Photoshop tutorials wanes, that is when I turn my attention to
better understanding my equipment. I know that if I am going to eat
photography I have to first live and breathe it. So far I keep pushing
the camera buttons but no pellets are dispensed.
Put another less silly way, I want to produce the best photographs ever
and this is a way to stay focused on photography whenever I get tired
or otherwise. I understand that there is baggage produced by failing
publicly, e.g. you and Johan probably think I am a dipsh#t, but putting
my ideas out there and having big brains hammer on them - I think is
faster.

Brgds,
Ron

Johan W. Elzenga

2006-08-23, 6:17 am

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

> Put another less silly way, I want to produce the best photographs ever
> and this is a way to stay focused on photography whenever I get tired
> or otherwise. I understand that there is baggage produced by failing
> publicly, e.g. you and Johan probably think I am a dipsh#t, but putting
> my ideas out there and having big brains hammer on them - I think is
> faster.

I don't think you're a dipsh#t, but I do think it's also wise to try to
understand what those 'big brains' are trying to explain to you. Getting
advise becomes pointless if you don't want to listen to it.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-23, 6:17 am

> I do think it's also wise to try to
> understand what those 'big brains' are trying to explain to you. Getting
> advise becomes pointless if you don't want to listen to it.
>
>
> --
Not understanding is unwise? That's being generous. Mix in
gregariousness and hypersensitivity and you end up with someone that
can really put the bug on some people. I suspect I am many lifetimes
away from wisdom. To be more frank this is more likely an issue of
aptitude than wisdom but regardless, like I tried to explain earlier, I
cannot change who I am.

Brgds,
Ron

Johan W. Elzenga

2006-08-23, 6:17 am

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

[color=darkred]
> Not understanding is unwise? That's being generous.

No, you can't be blamed for really not understanding something. What I
said was: You should at least *TRY* to understand. From your responses I
get the impression that you simply dismiss any advise that doesn't
confirm what you want to hear.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-23, 10:16 pm

> said was: You should at least *TRY* to understand. From your responses I
> get the impression that you simply dismiss any advise that doesn't
> confirm what you want to hear.
>
Now I see, and I take your point. But it only seemed like I wasn't
trying because I thought discussion of wb was tangential. I liked
having your input and I wanted you to continue to feel included in the
conversation without telling you that you were off task. It was
misguided but sincere. I am still worried that if I say the wrong
thing you will take your ball and glove and go home.
After more research, my current thinking is that in order to develop a
low cost system of calibration begins by using the camera to set black
point. I think by skipping that step all else if futile. I decided to
gloss over that issue early on but it keeps rearing its ugly head. Do
you think it's possible?

Thanks,
Ron

Johan W. Elzenga

2006-08-23, 10:16 pm

ronviers@XXXXXXXXXX <ronviers@XXXXXXXXXX> wrote:

> Now I see, and I take your point. But it only seemed like I wasn't
> trying because I thought discussion of wb was tangential. I liked
> having your input and I wanted you to continue to feel included in the
> conversation without telling you that you were off task. It was
> misguided but sincere.

Thank you for illustrating my point. I tried to explain to you why it
won't work what you were trying to do, so I'm misguided.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

ronviers@gmail.com

2006-08-23, 10:16 pm

> Thank you for illustrating my point. I tried to explain to you why it
> won't work what you were trying to do, so I'm misguided.
>
While I do not think you are misguided, your reply leaves open the
question of, if you think it is possible to set black point using the
camera.
After sleeping on it, it seems to me it should be fairly straight
forward to calculate the exponent of the gamma function by taking the
difference of the difference of the knob position, which should be the
bias of the transistors on the yoke of the CRT - and linear, with the
measured brightness of the display. This could be done by selecting
say ten knob positions (biases) and taking say twenty five photographs
at each position of say twenty five neutral, RGB=0, RGB=10, RGB=20...
RGB=250, images. Does that make sense?
Then just guess at the black point by using one of those online tone
charts or even Adobe's GCP black and gray square test.

Thanks,
Ron

KatWoman

2006-08-26, 6:16 pm

<ronviers@XXXXXXXXXX> wrote in message
news:1156357496.948709.174290@b28g2000cwb.googlegroups.com...
>
> While I do not think you are misguided, your reply leaves open the
> question of, if you think it is possible to set black point using the
> camera.
> After sleeping on it, it seems to me it should be fairly straight
> forward to calculate the exponent of the gamma function by taking the
> difference of the difference of the knob position, which should be the
> bias of the transistors on the yoke of the CRT - and linear, with the
> measured brightness of the display. This could be done by selecting
> say ten knob positions (biases) and taking say twenty five photographs
> at each position of say twenty five neutral, RGB=0, RGB=10, RGB=20...
> RGB=250, images. Does that make sense?
> Then just guess at the black point by using one of those online tone
> charts or even Adobe's GCP black and gray square test.
>
> Thanks,
> Ron

I think if his GOAL is to be a better photographer he will not find it in
being so intensely focused on so much technical specification.
Some great technical photographers suck at being creative.
(not saying this is true of the OP)

As you can fix the white balance in like a second afterwards it seems like a
huge waste of time to me all this messing about with paint and cards that
could better be spent building your artistic skills or taking pictures or
learning retouch and to makes prints. (I promise ron, this will be confusing
too, in terms of color setups)

ronviers@gmail.com

2006-08-26, 10:16 pm

> As you can fix the white balance in like a second afterwards it seems like a
> huge waste of time to me all this messing about with paint and cards that
> could better be spent building your artistic skills or taking pictures or
> learning retouch and to makes prints.

I am not too hard on myself about how much time I spend taking pictures
and editing because I spend a good bit of time on each but I agree that
my time could be better spent. Do you have examples of tasks or
exercises that will help develop and refine my artistic skills?

>I promise ron, this will be confusing
> too, in terms of color setups)

I have steeled myself for a lifetime of confusion. I finally realized
that if my I beat myself up about it then blocks set in and progress
stops.

Thanks,
Ron

KatWoman

2006-09-03, 6:16 pm

<ronviers@XXXXXXXXXX> wrote in message
news:1156642309.068836.283320@h48g2000cwc.googlegroups.com...
>
>
> I am not too hard on myself about how much time I spend taking pictures
> and editing because I spend a good bit of time on each but I agree that
> my time could be better spent. Do you have examples of tasks or
> exercises that will help develop and refine my artistic skills?
>
>
> I have steeled myself for a lifetime of confusion. I finally realized
> that if my I beat myself up about it then blocks set in and progress
> stops.
>
> Thanks,
> Ron

the easiest way to learn any skill is by doing not talking
and reading tips will take you just so far
practice
and OBSERVE
look at light and shadow
learn to know what looks good on the subjects you choose
if you don't have a specialty think about what part of photography or life
is exciting to you, just shoot that for awhile, get good at one thing, then
branch out
take lots of images
never throw away a happy accident
edit carefully
sometimes the mistake you make is worth repeating
figure out why an image looks good or nasty
is it close to what you wanted? can you make it more so by PS tweaking?

in the dinosaur times we didn't have the benefit of so much after-market
tweaking we had to learn to get it right the first time (in the camera)

open PS and play around on a copy of your image with all the tools to see
what they do, or even start with blank white image and see what you can make
in PS without a photo. I found a lot of stuff "by accident" I found the
creative playing very inspiring.
Study good work by photogs and digital artists you admire, see how they
light, compose subjects, emulation or copying "the masters" is another valid
learning tool.
If you get so confused by technical details you lose alot of the fun
artistic part
Just concentrate on the technical details for that one thing you are doing
that day, do it over and over till you know it without directions
Decide if you prefer to set up your shots or find your shots
Things, places or people? loose soft style, telephoto, romantic or bright
saturated wide angle, realism or fantasy.
Amateur or commercial work?
artistic or documentary?
Paint is messy
don't be overly perfectionistic, fear of failure can be crippling
everyone good had a learning curve
no artist is ever "done" there is always the hunt for that next "better"
image,
for capturing that one moment, there is no end to learning