How to remove a color cast besides just using adjustments>auto color?

hum,

Depends on exactly what you want to do, curves, hue/saturation, selective colour ad the channel mixer are the tools I favour. Which one to use depends on what exactly I need to do.

Does auto color overall do a good job of removing most color casts?

try the color balance adjustment sometime, set on an adjustment layer.

here’s 2 methods from my tips file gathered from here:

method 1:

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Color Cast
Here is another method that works well on images that have a color cast, especially if uniform across the image. Using the eye dropper tool sample an area where you can see the color cast. Next create a new empty layer. Fill this new layer with the foreground color you just sampled. Now Image>Adjust>Invert to invert the color. Now reduce the opacity of this layer until it cancel out the cast. When you have the color right, flatten the image (or create a new layer, then Ctrl+Alt+Layers>Merge Visible to merge the two layers onto a new layer).
Adjust the contrast by doing a levels command and pull in the sliders. You may also want to do apply Unsharp mask if it needs a bit of sharpening. Addendum:
d. wade thompson – 02:35pm Feb 14, 2003 Pacific (#7 of 7) Edited: 14-Feb-2003 at 02:35pm PST Hey Dave,
that technique you described works even better if you change the layer blending mode of your new layer to overlay and then adjust the opacity

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method 2:

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George Austin – 11:02pm Feb 22, 2003 Pacific (#22 of 22)

Jerel,

Not to advocate any one particular way of removing a color cast, but if you choose to do it with a multiplying layer as has been discussed, that method is perfectly capable of removing ANY cast. To remove:

RED: use 0/255/255

GREEN: use 255/0/255

BLUE; use 255/255/0

YELLOW: use 0’0/255

CYAN: use 255/0/0

MAGENTA: use 0/255/0

The role of opacity in blending is easily misconstrued. Only in the NORMAL blend mode does it act conventionally (or perhaps I should say intuitively). In most other blend modes, the opacity is nothing more than a throttle on the effect.

The Multiply blend has no effect at all at zero opacity. As you increase opacity from zero, the resultant color value in channels for which the layer color value has been set to zero is reduced more and more. The color value in layers set to 255 are totally unaffected by the Multipy mode—not even by the opacity setting in that blend mode layer.

You CAN use a non-zero value in the tint color channel(s) and that will change the opacity needed to counter it. But it is pointless to do so (as well as inconvenient) because all possible outcomes are achievable with just the opacity adjustment and only the opacity is adjustable via a slider. Adjusting the color value in the tint channel(s) would be a tial-and-error procedure. And the optimum opacity setting will vary with that color setting. Best to leave the color at zero. As a bonus, that provides a wider range of adjustment.

Again, I’m not pushing, selling, advocating, or what have you. Just trying to explain what’s happening in this interesting but not crucial approach. Understanding never hurts and may prove useful in other future scenarios. If you’re a teacher, your horizons ought to be a little broader than just getting the job done.

George
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regards, dave

Thanks everyone

Curves (Ctrl+M) is a great tool. Using the color picker, find your darkest and lightest points.
Then select a "gray" area (if your picture doesn’t have one, this won’t work to well). You may
have to "Ctrl + Z" a few times and try again in various places until you get the desired result.

Also, (Ctrl+L) adjust each RGB point in Levels (the middle slider).

Leppod~

wrote in message

What other ways are there to remove a color cast besides just using adjustments>auto color?

Also, clicking on a known neutral grey area in the picture with the grey eyedropper from the Curves or Levels dialog boxes. Fine tuning can be done with the curves/histogram for individual channels. As with so many things there is no best method – it depends on the image and the fault.

Cheers – John