It is important to understand that different types of lighting will produce different ‘color casts’ to the light in a photograph. While the eye is great at correcting for color ‘on-the-fly,’ our cameras aren’t very good at the task of adjusting in mixed environments at all. This can result in severely yellow/orange pictures, or sickly green ones, depending on the lighting present at the location. Generally the approaches to correcting for mixed-environment lighting depend on how much control you will have over the environment. The solution isn't to do all of these things, but to know about each of them such that you can do one (or more) depending on the situations you encounter.

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Complete control

(These solutions assume complete ability to control the ‘non-studio’ environment where the pictures will be taken. Because of the nature of completely controlling a location, to some extent it also assumes a large(ish) budget, and a good amount of time to engineer the environment.)

• Turn off the ‘contrasting’ light source(s) - The first thing to look for is whether you can turn off one (or more) of the competing light sources. In terms of ‘easy solutions’ this is always what I look at first because if I am able to remove ‘offending’ light sources with the flip of a switch, I can often bring the color cast back to ‘normal’ (or close to normal anyway). On occasion I have even found myself turning off lamps and gaffers taping or clamping my own flashes inside of the lamp to provide the illumination of the subject from an ‘correct’ direction (such as when the lamp is in the frame so having it on would be expected).
• Overpower the ambient lighting - If you aren’t in a position to turn off the contrasting light sources, the ‘next best thing’ might be to simply overpower the offending light with your own light sources. This works best if you’re able to throw enough light to completely light the scene yourself (e.g. if you only have enough power to light the subject OR the background, but not the subject AND the background) this will be tough to pull-off. I’ve included this one because I know photographers who do the kinds of shoots where they have the time to engineer solutions like this. For those of us who work more ‘on-the-fly,’ or are hobbyists, it probably isn’t practical to completely engineer the lighting in this manner.
• Gel everything - This is the ‘Hollywood’ solution for using practical locations and if you look at many ‘behind the scenes’ extras on DVDs you can often see combinations of gels being used everywhere… CTO gels on all the tungsten, CTG on the fluorescent, ND or CTB gels on all the windows, etc. While it often isn’t practical to gel everything, doing so will essentially ensure a proper color balance. I’ve included this one in the interest of completeness, but for ‘most of us’ this will be an impractical option short of working on a large-scale paid shoot (where this sort of thing is done all the time)…

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Partial control

(These solutions can often work in situations where complete control of the environment is not possible, but you do have some time to plan your photography at least a bit ahead of time or prepare the environment)

• Gel something - If I’m in an environment that contains 3 different types of lighting I may not have the time, materials, or wherewithal to gel everything… But if given the choice I’ll often choose to gel something. Generally speaking the thing that I try to gel is the fluorescents if possible because a picture with an orange color cast is easier to manage and looks more ‘correct’ to the eye. A picture with a heavy green color cast on the other hand… That only looks good if you’re in the Matrix.
• Control the angles - This will be situation dependent, but sometimes it’s possible to eliminate ‘offending’ light sources simply by not shooting in the direction of the light source. For example, I recently shot a wedding reception in a gym with lots of ugly fluorescent lighting up above, as well as one wall of the gym being all windows. The solution ended up being to balance for the fluorescents and simply not shooting anything with my camera pointing towards the windows (though admittedly not shooting towards the big bay windows was also because it was a daytime wedding and the daylight would have blown out all my pictures).
• White balance for the main subject(s) - If ‘all else fails’ and you have no other options available, at least white balance for the subject. This will (more or less) get the color cast right for the skin tones, which are the most important element of most pictures. The rest of the colors in the photo may be off, but for some photos this will be forgivable, and in others you have a few options still available to you in post.

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No control

(Though these can been solutions that are arrived at ahead of time, since they are post production solutions they can also be used ‘last ditch’ efforts, where either no color control was taken during the shoot, or the attempts at color control were not successful.)

• Convert to B&W - If you weren’t able to do anything to control the mixed lighting and/or the lighting came out in an unattractive way despite attempts to control it, one answer may be to simply make the picture black and white in order to remove all color cast.
• De-saturate in post - This is especially effective in situations where tungsten lighting has made pictures too orange. Often it can be an easy fix to simply ‘desaturate to taste’ and add a bit of blue (to tone down the pinks that invariably result from the desaturation).
• Mask the area(s) with improper color cast and rebalance them - Time consuming, but certainly an option if you have pictures that you need to keep, but the color cast is wrong. It is possible to come up with something relatively good looking by correcting the photograph for skin tones, and then using masks to further correct any areas where the remaining color is off.

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