Removal of Blue Cast

[krillen]

I have a severe blue cast in one of my pictures and no matter how I

adjust my curves etc I can't get rid of it and maintain the picute

colour quality. any suggestions?

[krillen]

Without re-scanning?

[._kaa]

Hard to tell without looking at the picture, but slight to moderate blue cast should be fixable by careful tweaking of global curves, or, in harder cases, by using masks and localized curve tweaking.

 

As a general technique, find a known black spot, a known white spot, and a known neutral grey spot (better if several) in your image, look at their RGB values, and then arrange the curves so that they all become neutral.

 

Of course, in case of a *severe* blue cast much of color information might be lost beyond recovery. Think about a blue-tinted monochrome picture -- you can treat it as an extreme case of blue cast and while you can take the blue cast away, you cannot reconstruct the colors since they are not there.

[jim h1664876971]

I wouldnt bother with curves I would adjust it using color balance sliders. I have

done some old slides from the 50s and they came up nicely using color balance.

[j_a]

I agree with Mr. Heathcott, but I would add, try going into hue/saturation, selecting blue and adjusting the hue.

[alan_schietzsch]

It all depends how severe the cast is. If it's moderate, a Color Balance

adjustment layer is a non-detructive solution you can easily change to suit

your judgement.

 

If it's truly a horrible cast, going into LAB mode will enable much larger color

shifts than are practical otherwise; you can recover photos that you'd think are

lost forever. Just work on a COPY - it takes "some getting used to" the radical

nature of even very tiny changes, when in LAB color space.

[krillen]

Thanks for the help. I'm a totally self taught PS'er so often there are little things I miss, so with the suggestions given by you guys I pulled two of the four shots into correct colour balance. Thanks again.

[sc21]

Just tonight I was working on a picture of a white boat in evening shade before a sunset-lit wooded shore and golden reflections. The boat was totally blue, and after much fuddling around in Elements, the way I got it back to even with the background was to use the magic wand color picker and then brush selection to outline the whole boat and its reflection, then Color Cast to bring the boat back to white, and finally Levels to bring it up as bright as the background.

 

For your case, you'd be working with the whole picture, so just try Color Cast - it works for me most of the time if you can find a white or grey piece to click on.

[sk_arts]

Well, I'd use levels and bump each handle over to the start of the histogram, or,

where the "mountain" begins.

 

90% of the time there is enough data to work with, even in the most severe cases. You

may need to rescan and do this correction in 16-bit, which i would suggest BTW.

Unless the other channels are completely empty or lack so much hilight or shadow

detail that there is just nothing there, period, even if you cannot visually see it right

away, you will almost always have *something* there. The only time I had this happen

was when I over exposed the blue pass on my Leaf scanner...

 

Typically images with a cast have channels which are thin or thick, but the data is

burried in there. Is the data as good as if you had a cast-free image? Ofcourse not,

but you can usually pull a very decent image from it.

 

If the red and green channels are entirely empty, there is something else wrong.

[sk_arts]

Oh, and the L*A*B* idea is a very good one. L*A*B* lets you adjust color without

affecting luminosity. Very benificial in extreme cases.

 

Be warned though, if you have never used L*A*B* it can be a very odd experience :)