How to recognize different lighting color temperatures?

Question

I'm getting my first "real" flash soon, and I've been studying a bit about lighting techniques. However, the flash comes with little colored plastic covers to match the color of the environment's lighting, which has me wondering: how am I supposed to tell which one to use? I suspect I can't just keep relying on auto white balance.

Of course, I could just take test shots and adjust until I get it right. But is there a trick to determining whether the room I'm standing in is lit by tungsten lights vs. fluorescent (vs. any other stuff)? I don't feel like I can "see" what the temperature is--is this something that I just have to train my eyes to detect? If so, what should I be looking for?

Answer 1

To some degree, you can see it, if you practice. Your brain automatically corrects, but you can learn to distinguish the different "feeling". That's not my main advice, though. Mostly, you can guess pretty well by where you are.

• At a home: mostly incandescent, but of course more and more people have CFLs, and unless they're particularly obsessive, probably cheap low-CRI CFLs. In homes, these are usually warm-balanced, and modern auto-wb often does an okay job. Some people are moving to LEDs, which right now tend to be a little cooler, but I expect warmer ones to be more popular — and, we can hope, better color rendition becomes a more common priority as brands start to compete on more than price.
• In public buildings or businesses: the light? it's fluorescent. Your only question is how cheap they are and whether they're glaring harsh white or one of the other common tints.
• Outdoors: varies, but if it's sodium vapor lighting, the color rendition will be so poor that you can tell — I'm sure you already know the characteristic orange/pink pallor. Halogen — basically, cooler white than normal incandescents but full spectrum — is common in floodlights. You'll find some fluorescents too, and LED lighting is becoming more common outdoors, usually easily recognizable as accent lighting.

Answer 2

Short of using a dedicated color meter that can run anywhere from hundreds to thousands of dollars, the best method I have found is to take a set of test shots that includes the ambient light in one and the flash in the other. Set the camera's WB to "Flash" or 5500-6500°K (if that is the color of your flash's output, which will vary slightly depending upon power level/duration) for both test shots. Then compare the color of the ambient light to the flash, which should show up as white. If the ambient light is rendered as a warm yellow/orange, you are looking at tungsten lights. If it is a greenish shade, then you are looking at fluorescent lighting. If it is an obnoxious washed out orange, you are dealing with sodium vapor lamps.

In order to filter the flash correctly, the color of the filter you place on the flash should match the color the ambient lights are rendered when the camera's white balance is set to the color temperature of the flash. Once the flash is filtered to match the ambient lights, you can then adjust the camera's WB to match using either the correct color temperature or a custom WB generated by shooting a white or gray test target. I prefer the custom WB method. Now both the flash and the ambient light should be rendered as white.

Answer 3

The easiest way is to look at what the bulbs look like, though this doesn't always work. You can get to the point where you can identify at least the most obvious versions of different lights, but some are tricky because they alter the frequency of the light with filters. The safest bet is always going to be to try it and see if there is a jarring difference between ambient light and the flash.