If you've been taking photographs long enough, you already have a basic understanding of color temperature, although the specifics may not be completely clear to you. Generally speaking, color temperature has to do with white balance - it's why you may notice that photographs you shot indoors under incandescent light have a bit of a yellow tinge to them, while photographs you shot in overcast conditions or in the shade may look a little bit blue.
Your white balance setting
If you're still a beginner, it's probably going to be enough for you to just understand color temperature in basic terms. Your auto white balance setting, most of the time, is going to do a pretty good job of rendering correct color, although you may find there are some situations where it isn't as good as it is in other situations. For example, if you're taking a photograph on a cloudy day and you see that blue color cast in your photos, you can just manually set your white balance to the cloudy setting, which should in most cases do a pretty good job of eliminating the color cast.
You may also have the opposite problem in some situations—for example, when you're shooting the sunset you may find that your camera overcorrects the color and instead of a brilliant red sky, you get sort of a pale, washed out yellow sky. In this situation you will also want to use that cloudy white balance setting—in order to correct for the blue cast in a cloudy scene, your camera will add warm red tones. So if you use that same setting for a sunset, your camera will actually add reds instead of trying to counteract them with blues, and the result will be a more brilliant sunset.
These are general ways of coping with white balance, and they work well most of the time, an exception being when you're in a mixed lighting situation. A mixed lighting situation is what happens when you have two different sources of light—natural light tends to have a slightly blue color to it, while incandescent light has a yellow color to it, and when you get both of these together in a room (for example, when you've got the overhead lights on but there's also sunshine coming in through a window), you get a mixed lighting situation, which may be difficult for your camera’s auto white balance setting to cope with. There's also no manual white balance setting for mixed light, so you'll have to set a custom white balance instead. All cameras do this a little bit differently, but generally speaking the process involves filling the frame with something true white such as a white piece of paper or a photographer's white card, taking a photo of it, and then telling the camera to reference that photo as the white point for the image. This works pretty well for mixed lighting situations, although you may have some parts of the scene that will still have a color cast, depending on how strong each individual source of light is.
cast a shadow by Flickr user sinkdd
The Kelvin scale
Beyond this, an understanding of the specifics of color temperature can help you achieve even more precision with the colors in your photographs. Color temperature isn’t just measured in presets, there’s a scale that we can use to assign value to different types of light (called the “Kelvin” scale). Let's take a look at a color temperature chart so you can get an idea of how different shooting situations correspond to Kelvin measurements.
As you can see from this chart, there are pretty significant differences even between the shooting situations that we would normally lump together as being warmer or cooler. For example, the light from a candle flame is significantly warmer than the light at sunset, which is warmer than the light from an incandescent lightbulb, which is warmer than moonlight. Yet all of those different light sources are on the warmer end of the Kelvin scale, so dialing in that color correction using the Kelvin scale is going to give you more accurate color than simply choosing the “incandescent” setting from your white balance presets.
One way to keep all of this in your head is to remember that dimmer light corresponds with lower color temperatures. So the dim light of a candle is around 1000 K, while a bright sky is 10,000 K. But it may be just as easy to carry around a picture of the Kelvin scale in your camera bag, or even download an app that will give you ready access to this information.
In order to make use of the Kelvin scale you do need to train yourself to notice the light. That means switching out of auto white balance and really paying attention with your eyes. That Kelvin scale can help you know what number to dial in in certain lighting situations, but it may also help you actually notice the differences in the color of light with your own eyes.
Start with the Kelvin setting that corresponds to the light that you know is in the scene—in your own home, for example, you will likely have a mix of window light and incandescent light at regular times of the day, and if the lighting in your home is consistent you will probably be able to use the same Kelvin number for anything you shoot in your house. You can also use precise increases in Kelvin to control those colors in the sunset—for example, if the cloudy white balance setting creates a sunset that looks a little too red for you or not red enough, you can change the Kelvin setting instead.
Not all cameras give you the ability to change Kelvin specifically, so check your camera’s manual. Chances are you will find this setting under white balance, listed after all of the white balance presets. Once you select the Kelvin or “K" white balance preset you should be able to use a dial on your camera’s body to change that Kelvin number incrementally. Again, make sure you've got your Kelvin scale somewhere handy so that you can precisely judge how much you'll need to dial in for the shooting situation that you find yourself in.
Now you may have just read through all of this information and are still asking yourself “why?" You may have heard that if you shoot in RAW, you don't have to worry too much about color temperature because you can always correct color temperature after-the-fact in post-processing. And while this is true, it is also true that using an incorrect white balance or Kelvin temperature may actually affect your exposure, so you may lose tonal range when you correct the white balance after the fact—not to mention the added hassle of having to go into post-processing every time you take a photograph.
If you don't find yourself shooting in RAW very often anyway, then it pays to have the white balance correct in camera. Remember that shooting in RAW means the post-processing for every single image you take, and not everyone is prepared to do that just to avoid the hassle of having to set the white balance or Kelvin temperature for each image. This becomes even more true when you're talking about those minor differences between, say, a cloudy day and a day that is heavily overcast. Your white balance is going to be a lot more accurate if you use the Kelvin scale to change it than it will be if you simply dial in the cloudy white balance setting. The cloudy white balance setting isn't going to account for those very real differences in color temperature between a heavily overcast day and one that is just cloudy.
Heavy Clouds by Flickr user chibitomu
Remember once again that you don't always want perfect white in every photograph you take—there are plenty of situations, such as the sunset we talked about above, where you may want to add color using that Kelvin scale in order to create a sense of drama or a certain mood in your image. So always evaluate the scene first, before you decide which Kelvin temperature to select, to make sure that you even want to get that perfectly white white. It could be that having a neutral white in your photo will take away some of the emotional impact of the image, and that's not what you want, even if it's in the interests of perfection.
I realize that at first this can all seem a little intimidating, and I understand why. Anything that involves numbers and words like "Kelvin" and "temperature" can sort of end up in the same realm of photography words like "lens diffraction" and “histogram" as stuff you kind of just don't want to deal with when you’re a beginner. But processing this information really is not that difficult—it truly is just a matter of studying that chart and learning which light sources correspond to which temperatures. And you don't even have to do that, really—a simple printout in your camera bag or, as I said, an app for your phone, will give you the information you need if you're ever in doubt.
The one thing that you do need to remember is to make these changes every time the lighting situation changes—I can't tell you how many times I have forgotten to switch back to the correct Kelvin setting for a new situation and ended up with a set of photos that were way too blue or too red. It's an easy mistake to make, so some diligence is called for. But once you get the hang of it and make it a part of your routine, you'll start to notice that the beauty of those precise colors contributes to an improvement in the photographs you shoot in almost any lighting situation.
- White balance setting
- Use your presets
- Set a custom white balance in mixed light
- The Kelvin scale
- Different lighting conditions correspond to different Kelvin numbers
- Dimmer lights correspond with lower temperatures
- Learn to notice the light
- Use Kelvin to account for minor differences in types of lighting
- Don't count on being able to fix white balance in RAW
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