Photographers of a certain age, like me, have been struggling with what we now know as white balance for as long as we have been making color photographs. Like so many technological changes, the control over white balance that comes with digital imaging is a blessing and occasionally a curse. I was reminded of this when I tried to answer a question posed to me recently about that very complex issue.
The question came to me from a friend:
I am helping out a friend who is doing a project on female boxers. Some of the events she has shot were in large gyms at schools where she can’t always use a flash because it distracts the fighters. She is having a big problem with deathly yellow color-cast. I am assuming the lighting is a combination of florescent and incandescent.
First, how tech savvy is your friend? The best way to do this is figure out the custom white balance for the bulk of the ring and use that as a starting point. White balancing off a grey card is best though working off of white paper works well too.
Though you can shoot RAW files and try to color correct the images after the fact that is not the best strategy. As you can imagine, correcting after the fact means that you will probably be able to correct for one part of the color cast but not another, so you are always “chasing” the perfect white balance. Getting the white balance right (or close to right) in the camera during the capture will go a long way towards getting rid of most (or all) of that color-cast.
Each camera is slightly different but in all cases what you want to do is find the custom white balance setting on the camera. With that turned on, you take a photo with a grey card, (or a sheet of plain white paper,) filling most of the frame with the card or paper. Make sure that the card or paper is in the same light as what you are trying to color correct. The most common mistake many people make is that they cast their shadow on the paper/card, thus getting an incorrect color sample. The camera takes that neutral white or grey in the test image and corrects until it is “clean,” without any of the annoying color-cast. That is custom white balancing, in essence.
In the worst of all worlds, there maybe more than one white balance in the same place, in this case, there maybe a different one for each corner of the boxing ring. Correcting for that would take a lot of changing of the white balance setting on the photographer’s part each time she changes places she is photographing. Or she might consider using multiple cameras set up with a different white balance on each camera as she moves around.
In either case, while she is photographing, she should, periodically, photograph a grey card (or piece of white paper) ideally in the exact same light as her subjects. With that she can then do a bulk correction to get the right white balance on all the images that were made in the same place.
A few more things to keep in mind:
1) Are the exposures perfect for RAW files? Meaning a bit overexposed and thus having the most information possible?
2) Has she considered using a fixed focal length, large aperture lens, such as a 50 mm f/1.8 lens. That will enable her to use a lower ISO to get a better exposure and file quality. It will also leave her backgrounds out of focus, which will make the odd color-cast less of an attention draw.
Those two steps would go a long way to getting better images with more tolerable color-casts.
Finally, the BEST way to solve this problem is to use electronic flash as the main light on the faces. The faces would need to be in the foreground close to the flash (and two or more stops darker than the background.) That way without the flash, the faces would be black. The light from the electronic flash that fills the faces in would be fast enough to stop the action and bright enough to be the only light on the faces.
The actual process is to white balance (as described above) for the background and set the white balance on the camera for that custom white balance. That white balance is the complementary color to the color of the background (canceling out that color-cast.) You also need to put some kind of filter over the flash so the flash is putting out the same color light as the background. That would result in having the flash filling in the face with a light that matches the background light and thus the color balance would be perfect.
The problem with this is that while finding the exact white balance for the background it is easy, it can be difficult to have exactly the right filter to make the flash the same white balance as the background. What I do is work with a couple of filters for my flash with the most common white balances that I have found recur over and over. (See below.)
The biggest improvement, for the better, with digital cameras is that you no longer have to get an actual filter to put over the lens that is the complementary (opposite) color of the light of the flash and the background. The idea is that if the background is a hideous green, for example, you now use a filter to make the light coming out of the flash the same green. In the bad old days you also needed a filter over the lens that was the complement of that green, in this case it would be magenta. But today you only have to set the white balance on your camera for the custom white balance, the complementary color to that background. In this case that complement would be magenta, to cancel out that green. The challenge is that most times the lighting is mixed so getting the exact filters for every weird combination of light is very hard, if not impossible.
What I do is carry two filters that I can put over my flash that cover 95% of the situations that I encounter. One is a CC (which means color compensating) 30 Green which turns the light from my flash the same hideous green as 95% of the fluorescent lights that I encounter. The light comes out of the flash green, which matches the background. Then the white balance in the camera is set to the equivalent of a CC 30 Magenta, which is the complementary color that cancels out that green, on the subject AND the background. I have the exact same set up for tungsten light with an orange gel to go over my flash so the flash and the background light are both excessively “tungsten light” orange. The white balance on the camera is set for tungsten light, meaning a kind of blue, which cancels out that tungsten orange.
For someone who works with many different qualities (and colors) of light, the white balancing capability of digital imaging is by and large a blessing. I no longer need to carry around many filters to change the white balance of the light that hits the sensor (in the old days film) in my camera. That is an upside of changing technology.
The proliferation of weird light sources with crazy color balances is the technological flip side, a technological innovation that has not been so good for photographers. The explosion in new lights includes mercury vapor lamps, florescent bulbs with varying color temperatures and sodium vapor lamps among others. Many are improvements in terms of light quality and energy use but they have made the work of photographers much more challenging.
One downside of white balancing capability of digital imaging is that the monitor on the back of your camera immediately shows you what is wrong in terms of white balance and if you become obsessive, like me, you can spend a great deal of time and energy chasing the perfect white balance.
In some ways, the bad old days of film were almost better. You balanced the light as best you could, took your pictures and were satisfied with what you ended up with. In a weird sort of away, not having that immediate feedback of the digital camera monitor was a kind of ignorance. And, as they say, ignorance can be bliss.