Computer Graphics with Photoshop - Removing colour hue

Author

Removing colour hue - please help

Neil Hindry

2005-05-19, 7:14 pm

I wonder if you can help me.

I have a few old photographs that I want to repair and they have a very
heavy red hue.

What is the easiest way to get rid of the heavy red hue that is spoiling the
photographs and make them look normal & natural again?
For information I am using PhotoShop 7.

I hope you are able to help me.

I appreciate any help or information given.

Thanks!

Neil

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Caitlin

2005-05-19, 7:14 pm

Mike

2005-05-19, 7:14 pm

"Neil Hindry" <n_nospam_hindry@_nospam_hotmail.com> wrote in message
news:428c851b$1$24474$da0feed9@news.zen.co.uk...
> I wonder if you can help me.
>
> I have a few old photographs that I want to repair and they have a very
> heavy red hue.
>
> What is the easiest way to get rid of the heavy red hue that is spoiling
the
> photographs and make them look normal & natural again?
> For information I am using PhotoShop 7.
>
> I hope you are able to help me.
>
> I appreciate any help or information given.
>
> Thanks!
>
> Neil
>
>
Quick and easy method -
Add a levels adjustment layer (or just go into Levels - CTRL-L). Select the
Black eyedropper and click on the point in your picture where the pixels are
darkest. Next, select the White eyedropper and click at the point in your
picture where the pixels are brightest. Finally - and this is the important
part - select the Greypoint eyedropper tool and click at a point in your
picture where the the pixels should be as neutral as possible (ie. mid
grey). This will either involve you having some knowledge of the original
scene (ie. knowing which part of the original picture should be neutral
grey) OR a large amount of guesswork. A tip - if it's an outdoor scene, look
for some pavement or a road surface, these are usually pretty accurate
mid-points. Avoid the temptation to choose a metallic object for a
mid-point, they may be grey but they often give pretty horrible results.

There are plenty of better techniques. If I can help any further, feel free
to email me.

Ctein

2005-05-19, 11:14 pm

Dear Neil,

Well, the easiest, but not cheapest, way is to get a copy of the
Photoshop plug-in, Digital ROC from Applied Science Fiction (a.k.a. Kodak
Austin Division) -- www.asf.com. It does a fabulous job of recovering old
photos like that, likely better than you can do manually. I use it in some
fashion on most of my commercial jobs.

Assuming you'd rather not throw money at the problem, here's the manual
approach:

1) Scan the photo in 16-bit mode if your scanner supports that. (If it only
supports 8-bit scans, do steps 2 and 3 in the scanner software tools, to
maximize tone and color information in your file.)

2) In Photoshop, find a part of the photo you're pretty sure should be white
(like an unexposed print border or a real white highlight). Use the Levels
or Curves tool to move the white endpoints until the RGB values for that
region are all equal and around 235 (which will be a very light gray, and
the reason we're not going for true white yet is so that you don't
accidentally clip highlight data).

3) Next find a part of the photo you're pretty sure should be true black.
Use Curves or Levels to adjust the black endpoints until that region has
equal RGB values down around 25.

4) The picture will probably have an overall color cast and be low in
saturation. If you can find something in the picture that was a neutral
grey, you can use that as a guide in Curves. Set midpoints on each of the
RGB curves and drag them up or down appropriately until the neutral tone
looks neutral. Now the overall color balance should be pretty good.

5) Pull up Hues/Saturation and kick the overall saturation up to about +20.

This should get you in the neighborhood. Have fun!

pax / Ctein

==========================================
-- Ctein's Online Gallery http://www.ctein.com
-- Digital Restorations http://photo-repair.com
==========================================

Rosanne Cleveland-King

2005-05-20, 7:15 pm

I use the NIK filter system with PhotoShop and find that it works
wonderfully with that sort of thing. I also use DCE tools for color
correction.

Smiles,
Rosanne

Geoffrey Pocock

2005-05-21, 7:14 am

Neil Hindry wrote:
> I wonder if you can help me.
>
> I have a few old photographs that I want to repair and they have a very
> heavy red hue.
>
> What is the easiest way to get rid of the heavy red hue that is spoiling the
> photographs and make them look normal & natural again?
> For information I am using PhotoShop 7.
>
> I hope you are able to help me.
>
> I appreciate any help or information given.
>
> Thanks!
>
> Neil
>
>
>
Hello

I sometimes find a numerical method useful. Look at the RGB values where
the image should be white. Say you find R=240, G=200, B=198. The Red
channel is 40 bigger than Blue and 42 bigger than Green. So, open a
levels adjustment layer and set the Blue highlights to 255-40 = 215, and
the Green highlights to 213.

You may want to do some averaging but I find if you so this it is a good
starting point.

Good Luck

Geoffrey

Geoffrey Pocock

2005-05-24, 7:17 pm