In previous posts in this series I’ve talked about what white balance is and how it can be used creatively, both in the field and in post production. In Part 1 we noted that if the camera’s WB setting matches the color temperature of the light hitting the subject; white, and all other colors, will be rendered correctly. And that we could change the mood or fell of an image if we intentionally used an “incorrect” WB to render the image warmer or cooler. But if colors can be accurate or intentionally changed which is correct? I addressed this question in Part 2 and gave two different approaches or strategies that can be used to determine which WB setting to use: Accurate and Creative. And in Part 3 we discussed how shooting in the raw format allowed for greater flexibility in setting any WB after the shoot. And that when shooting in jpg the photographer needed to pay more attention their camera’s WB setting during capture.
In this post I’m gong to discuss ways to determine what your WB should be set at.
Suppose you’ve hiked to a favorite location to capture the magnificent hues of a spectacular sunrise or sunset. But when the event occurs the colors don’t live up to expectations and the warm hues are more hints of color than spectacular and brilliant color. What can you do to “help” the image? Lie to the camera or converter and tell it that the light source has a lot of blue in it and the camera/converter will warm the image up. You can do this by setting the WB setting to Cloudy 
, for a little warmth, or Shade 
, to really warm the image up.
Or if you want your image to have a somber mood then you want to tell the camera/converter that the light source for the image had a lot of yellow in it. To do this set the WB for incandescent (or tungsten depending on what your camera calls it) 
. This will cause the camera/converter to shift the color bias away from yellow toward blue. BTW, as a side note, hollywood film makers have use the tungsten WB setting and underexposed by one or two stops to make scenes shot during the day look like they were shot at night. Try it.)
But what about the case where we want colors rendered accurately? Using your camera presets will only get you in the ball park. This is because the presets are for one specific color temperature. And there can be a great deal of variation in the color temperature of a light source. For example, the color temperature of the light coming from a light bulb varies with hours of use. As I said these setting will get you in the ball park (certainly closer that Auto WB). So in most instances this all you need. But what about those cases where you need a more accurate WB, like in the studio shooting portraits? For this case there are a couple of classes of tools that can be used to get a more accurate WB setting:
- Those that use reflected light
- Those that use incident light
When using either of these types of tools you use it to set a Custom or Preset White Balance that you then use to shoot the scene. Since the procedure for doing this is different for every camera (even from similar camera from the same manufacturer) you will need to refer to your camera manual to find out how to do this. (For example the procedure to set a Preset White Balance on the Nikon D40, D50 and D60 cameras are all different).
To use the reflected light technique you need a color neutral (not necessarily white or black but any tone of gray that is made up of equal part red, green, and blue). In a pinch you can try a plan blank sheet of paper but it will most likely not be exactly color neutral. If you have a gray card left over from your film days you can use that. (I’ve read where some folks have gotten bad results with a gray card. And I suppose this is possible as the gray card is designed to be use to set exposure. And as such it needs to be tone neutral and could have a color cast even though it looks gray to you and I. I personally have had great success using my gray card. But that is a sample size of one.) Or you can buy commercially produced cards like the WhiBal card. (BTW, these card can be used to set WB during the raw conversion process. Simply put the card in the scene and shot one photo. Then shoot as much as you like so long as the light doen’t change. Then when you get back on the computer, open the sequence in your favorite raw converter and select all the images, including the first one with the card, and using the converter’s WB tool and click on the card and apply that WB setting to all the images.)
To use the incident technique you need something opaque to cover your lens. You then put the camera near where the subject is and point the camera back at the light source (like you do with an incident light meter). You then set a Custom or Preset WB. Remove the opaque object and shoot. Inexpensive options include the top from a can of Pringles or a coffee can. I’ve even heard that a Mr. Coffee filter will give good results. Commercial versions include the Expodisc. There is no doubt that you will get the best results with the Expodisc but if you don’t need to set a WB Preset very often maybe one of the other diffusion devices mentioned might work for you. And they are almost free.