An easy way to remove color casts - this is great!

I saw this tip the other day on another forum and thought I'd post it here. The tip came from Charles Glatzer. This is very easy to learn, and takes the subjectivity out of removing casts. The only "addition" I might add would be to experiment with the final step (#6). Don't just automatically go to 50%, but play around a little with it.

1. Duplicate the background layer (Ctrl J)
2. Select the duplicate bkgd layer
3. Filter > Blur > Average (produces a solid color matching the color cast)
4. Open Levels Adjustment Layer, click duplicate bkgd layer image w/ middle (gray set) eyedropper.
5. deselect layer visibility icon (eyeball) of duplicate bkgd layer
6. tweak adjustment levels layer opacity to suit taste (50% is norm)

Haven't tried it yet Bill, but this appears to make more sense than anything I do now.

In an elaboration I wonder about doing multiple layers of this to account for multiple light sources, then selectively applying them to the base image. That would save me bunches of time (and therefore money) in gelling stray light sources on some scenes.

Don't know about that Hank. haven't tried anything but the basic principle as yet, but it sounds interesting. Let us know how it works.

Having experimented with this technique (which works very well), I will add the you cannot record this entire process as a single PS action and apply it to subsequent images. The step #4 must be done on an image by image basis. You can record the steps as an action with a forced Stop at that step, apply the gray eyedropper, and then continue the action.

Bob is correct, You also cannot record it and use it as an Action if you choose to open the RAW file as a Smart Object through ACR 4.2 since the "background layer" is a specific individual file name instead of just being named "Background Layer".

Thanks for this excellent tip, Bill. I can see this will be a regularly used action.

Thanks for the tip Bill. I tried it, and it worked great with a few "problem" images I keep around for testing purposes. But it doesn't seem to judge color properly when using Singh-Ray GND filters. It seems to correct the color in the sky to more natural, but the non-filtered part gets a different greenish-bluish cast.

But the tip is helpful nevertheless.

I'll add it to my bag of tricks (and it's a good trick) but it's not an end all and be all solution.

Bill -
I'm following your steps through Step 3, but from there on, it makes no sense.
Why the eyedropper sample?
Shouldn't you be setting the blend mode of the duplicate layer to Overlay after doing an inverse to it?
And why would you do step 5 (deselect the duplicate layer) when you are applying it as an adjustment layer to the background?

Confused.

Thanks for posting this tip Bill, it's been really useful!

Mearle, since no one else has replied I'll take a stab at it. As I understand it, what you are doing with the duplicate background layer (steps 1-3) is calculating the overall (average) color of the image --when you go through the steps in photoshop you'll end up with a solid color layer with some cast (you can no longer see the original image). Then in step 4 you use the levels (or curves or whatever) layer to neutralize this overall color. But since the duplicate layer is a solid color you've got to make it go away so you can see the original photo, hence step 5.

Ana - I see that you neutralize the color cast of only the duplicate layer, then you turn off the duplicate layer, and you see the original unaltered layer again i.e. - back where you started.

Hi Mearle, are you sure you are creating an adjustment layer in step 4 (e.g. layer->new adjustment layer->levels) as opposed to applying the correction directly to the duplicate layer (e.g. image->adjustments->levels)? If you do it the first way then the levels layer exists independently of the duplicate background and the correction remains when you turn the duplicate layer off.

I tried this technique on some scans of Astia 100f 4x5 transparencies and found that the tip works pretty well. I did find that, in a couple of cases, I had to fine tune using a curves layer or a color balance layer.

The step that Ana mentions above is crucial. One must also make sure to click the 'grey' eyedropper in the levels dialog box before sampling the averaged image.

This is a nice tip and is certainly worth trying! Thanks for posting it, Bill!

-PB

Yes, I understand now. I finally got back here with an image I wanted to try this with. Cool!