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[OM] [OT] (slightly) Photoshop tip for color correction

Subject: [OM] [OT] (slightly) Photoshop tip for color correction
From: Scott Gomez <scott@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 9 Nov 2002 12:12:52 -0800
I'm trying to color-correct photos this morning. Old stuff, contributions
from an old shipmate, and badly color-shifted over the years. Overall color
casts were anything from a nasty brown to a blue "haze". I was having a
tough go of it, until I remembered there was a tip for color-correction in a
book I had bought. The book is "Photoshop Photo-retouching Secrets" by Scott
Kelby. I've think I've mentioned it here before.

Kelby's tip for making color-corrections makes it almost simple:

1. Open the curves dialog (image/adjust/curves). Make sure you've got the
"Preview" box checked, so you can see the changes happen in your image.
2. Double-click the left-most (black) eyedropper
3. On the resulting dialog set the following values: C:75, M:63, Y:62, K:100
and click OK
4. Double-click the right-most eyedropper (white)
5. On the resulting dialog set the following values: C:5, M:3, Y:3, K:0 and
click OK
6. Click the left-most eyedropper once.
7. In your photo, find a pixel that *should* be pure black and click once.
The image's colors *may* shift radically. Don't worry, press on.
8. Click the right-most eyedropper once.
9. In your photo, find a pixel that *should* be pure white and click once.
At this point, your image may be bang on. If not, and there's still a color
cast...
10. Double-click the center (neutral gray) eyedropper
11. On the resulting dialog set the following values: C:50, M:40, Y:40, K:10
and click OK
12. Click the center eyedropper once
13. In your photo, find a pixel that *should* be pure neutral gray and click
once.
14. Look right? Click OK in the curves dialog to apply the changes.

At this point, you should have an image that's *vastly* improved. The
eyedropper settings appear to be retained from session to session, making
this even quicker to perform next-time out. You can also adjust all three
"color points" repeatedly until you get what you want by repeating steps 6-9
and 12-13, as long as you don't proceed to step 14 until you're satisfied.
You can compare an original and the result here:

http://petroglyph.crestline.ca.us/colorcast.htm

(Note that this page is NOT linked in to the rest of my site, you can't
navigate to it from there.)

Unfortunately, I don't believe this particular tip applies to Photoshop
Elements, as I don't think it's got CMYK adjustments. It does apply to
versions of Photoshop starting with version 5. You *may* be able to achieve
something similar in Elements by manipulating the values you *can* change,
assuming there's a curves dialog.

As far as I am concerned, this one tip paid for the book, and I've found
other equally useful ones in it, also. Can't recommend it highly enough.

---
Scott Gomez

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