Using curves to correct color tints

voodoocat

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In response to this thread, i posted a table that shows how to correct color tints.

If the image is too:
Red - Decrease the amount of red
Green - Decrease the amount of green
Blue - Decrease the amount of blue
Cyan - Increase the amount of red
Magenta - Increase the amount of green
Yellow - Increase the amount of blue

This can be accomplished using the curves tool in your favorite image editing software. This tutorial uses screenshots from Photoshop but can be done in PSP, Gimp, and most image editing applications.

We start out with this shot taken on Fujichrome Astia. The film was in the bargain bin. I only paid $0.50. Being old pro film that was not refridgerated, I'm not sure this is how Astia would normally perform. At the time I was pretty ignorant of slide film and didn't even realize it was such.

original.jpg

There is a slight blue cast on this image.

Let's fire up the curves menu to fix that.
curvesmenu.gif


We are going to select the blue channel from the drop down menu. Click and drag the center of the curve to adjust this channel.
bluechannel.gif


Such a small change that has a dramatic impact on the image.
lowerbluecurve.jpg

Looking good. Gives it a warmer look. It looks a little too warm though.

Here is another easy edit where you can achieve spectacular results. Using the droppers on the lower righthand corner, we define white, midtones and black.
usingblackgreywhitedroppers.gif


The first dropper is black. Find the darkest color of the photograph and click on it.
The second dropper is grey. Find a good midtone and click on it.
The third dropper is white. Find the whitest color and click on it. Don't settle with the first color you click on.

finalimage.jpg

For this edit, finding the black was easy. I used the darkest part of the shadow from the tree near the base. I tried quite a few different midtones and settled with the grey sidewalk tiles. For white, I used the highlight on the tree. After applying the edit, I went back to the blue channel and dropped it slightly.

Here is what I came up with earlier. I also increased the contrast of the image and used the unsharp mask.
 

drlynn

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Very nice, Voodoo. Thanks. I have found that for most of my photos, I only need to use the midtone dropper. Usually it effects enough of a change to cover everything. Occasionally I will have to use the other two, but try not to. I have found that the white dropper, especially can cause some color inversion.

Of course, it could be the fact that I'm PS self-taught :D !
 

terri

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This is great stuff for me.... I really appreciate it. I use PSP, but it doesn't matter what I'm fooling around with - when it comes to color correction, I'm in hell. :twisted:

I use a Daylab slide printer that also calls for knowing these basic adjustments. Some images just seem to be harder than others.

This was a great little example - thanks again!

In the meantime....practice, practice, practice..... *sigh*
 

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