Computer Graphics with Photoshop

Author

Curves question

Mike

2006-05-21, 10:20 pm

Hi,

I'm doing more and more of my Photoshop work in CMYK, as most of my pictures
are for print rather than screen viewing. When I come to write curves
adjustment layers, I like to switch the orientation of the graph to the same
as RGB - ie. black on the left.

However, when I click on the little black and white arrows to make the
switch, something happens. Instead of my sample point values showing as
percentages (as they should in CMYK), they revert to RGB (ie. 50% becomes
128). This only happens after I switch the orientation of the graph - before
making the switch I get normal CMYK percentages.

I know I am missing something pretty straightforward, and I know I'm going
to feel stupid when I get the answer. But it's late, I'm tired and I'm
willing to feel dumb in order to solve this!!

Thanks in advance.

Mike Russell

2006-05-21, 10:20 pm

"Mike" <noot1967@yahoo.co.uk> wrote in message
news:e4r140$l27$1@nntp0.reith.bbc.co.uk...

> I'm doing more and more of my Photoshop work in CMYK, as most of my
> pictures
> are for print rather than screen viewing. When I come to write curves
> adjustment layers, I like to switch the orientation of the graph to the
> same
> as RGB - ie. black on the left.
>
> However, when I click on the little black and white arrows to make the
> switch, something happens. Instead of my sample point values showing as
> percentages (as they should in CMYK), they revert to RGB (ie. 50% becomes
> 128). This only happens after I switch the orientation of the graph -
> before
> making the switch I get normal CMYK percentages.
>
> I know I am missing something pretty straightforward, and I know I'm going
> to feel stupid when I get the answer. But it's late, I'm tired and I'm
> willing to feel dumb in order to solve this!!

This is normal behavior. Photoshop is not reverting to RGB, but it displays
color values from 0-255 when you have black on the left, and 0-100 when
black is on the right. Black on the right takes some getting used to, but
this is the way the really cool people do it, since it indicates the amount
of ink.

The Curvemeister plugin allows this to be set independently, so that you can
have black on the left and still use ink percentages.
--
Mike Russell
www.curvemeister.com/forum/

Mike

2006-05-22, 3:17 am

"Mike Russell" <RE-MOVEmike@Curvemeister.comRE-MOVE> wrote in message
news:hP8cg.13472$fb2.9187@newssvr27.news.prodigy.net...
> "Mike" <noot1967@yahoo.co.uk> wrote in message
> news:e4r140$l27$1@nntp0.reith.bbc.co.uk...
>

> This is normal behavior. Photoshop is not reverting to RGB, but it
displays
> color values from 0-255 when you have black on the left, and 0-100 when
> black is on the right. Black on the right takes some getting used to, but
> this is the way the really cool people do it, since it indicates the
amount
> of ink.

Thanks for the reply Mike, good to know I'm not going mad! I now understand
that it's normal behaviour, but I still don't understand WHY Photoshop does
this. If I'm working in CMYK then I want percentages - why can't I have
percentages and use black on the left curves?

I'm working in CMYK after reading Dan Margulis's book Professional Photoshop
and he recommends setting CMYK and RGB curves so black is always on the same
side. I don't recall him mentioning this issue.
>
> The Curvemeister plugin allows this to be set independently, so that you
can
> have black on the left and still use ink percentages.
> --
> Mike Russell
> www.curvemeister.com/forum/
>
>

Mike Russell

2006-05-22, 3:17 am

"Mike" <noot1967@yahoo.co.uk> wrote in message
news:e4rcro$otb$1@nntp0.reith.bbc.co.uk...
....
> Thanks for the reply Mike, good to know I'm not going mad! I now
> understand
> that it's normal behaviour, but I still don't understand WHY Photoshop
> does
> this. If I'm working in CMYK then I want percentages - why can't I have
> percentages and use black on the left curves?

I agree with you, and added this feature to Curvemeister. Photoshop feels
differently.

> I'm working in CMYK after reading Dan Margulis's book Professional
> Photoshop
> and he recommends setting CMYK and RGB curves so black is always on the
> same
> side. I don't recall him mentioning this issue.

Just to keep you on your toes, in some cases Dan will show a composite image
with black on the right and the numbers going from 0-255 for RGB. This is
impossible to achieve in the real world, using Photoshop.
--

Mike Russell
www.mike.russell-home.net

Mike

2006-05-22, 10:16 pm

"Mike Russell" <RE-MOVEmike@Curvemeister.comRE-MOVE> wrote in message
news:aaccg.79830$H71.9575@newssvr13.news.prodigy.com...
> "Mike" <noot1967@yahoo.co.uk> wrote in message
> news:e4rcro$otb$1@nntp0.reith.bbc.co.uk...

>
> Just to keep you on your toes, in some cases Dan will show a composite
image
> with black on the right and the numbers going from 0-255 for RGB. This is
> impossible to achieve in the real world, using Photoshop.
> --
>
Thanks for the heads-up about that :-) I'll keep a look out for it as I work
my way through the book a second time - my mind is dizzy even thinking of
trying to figure out one of those curves!

Mike Russell

2006-05-23, 3:21 am

"Mike" <noot1967@yahoo.co.uk> wrote in message
news:e4tn8o$k9a$1@nntp0.reith.bbc.co.uk...
[re Professional Photoshop book]
> Thanks for the heads-up about that :-) I'll keep a look out for it as I
> work
> my way through the book a second time - my mind is dizzy even thinking of
> trying to figure out one of those curves!

I doubt anyone can get it all from reading. One effective way to learn is
to load the images from the CD and try the eamples yourself.
--
Mike Russell
www.curvemeister.com/forum/