Photography and Art

Thursday, June 4, 2009

White Balance and Gray Cards

One of the big attractions of capturing your images as RAW files is that you can adjust white balance afterwards so that your images don't have annoying colour casts. There are several ways of adjusting white balance using a tool such as Adobe Lightroom:
  • If the image has a gray or white area in it, you can take the white point eye dropper tool and click on that area in the image. Lightroom will automatically adjust the red, green and blue levels to make that area neutral.
  • If you have a handy gray card (like the WhiBal) and remember to actually photograph the gray card during your shoot, you can use the white point eye dropper tool and click on the gray card to get the appropriate white balance. This white balance can then be applied to all the other images in the shoot using Lightroom's sync feature.
  • The final technique is to use Lightroom's white balance adjustment control to set the white balance to something that looks pleasing to the eye. This technique only works if you have profiled your monitor. It's no use setting a white balance on a monitor that has a colour cast to it.
I was reading Tim Grey's daily e-mail today and he makes a great point about white balance:

"in most cases you are not trying to neutralize the color temperature of the lighting under which you were photographing. Quite the contrary, in most cases you were photographing when you were for the express purpose of capturing the warm lighting that was present at the time. As a result, in most cases it is not helpful to use a gray card as the basis of a white balance compensation. Instead, I would either use an "auto" setting for White Balance in your camera, or use the setting that seems to best match the existing conditions with the understanding that in any case you may need to apply a compensation in the RAW conversion in order to produce the most accurate (or desirable) results possible."

I don't blame you if you are confused at this point. When do you use a gray card and when don't you? Here's some guidance on when you'd want to use a gray card or adjust white balance using the eye dropper tool:

  • If you are taking indoor pictures of people or outdoor photos of people at sunrise or sunset and want a natural flesh tone, then you must use a gray card. Artificial light is notorious for fooling the auto white balance setting of the camera. Quite often, lights sources are mixed (e.g. flourescent combined with flash) and the camera won't know how to adjust for the resulting colour cast. Similarly, photos at sunset result in orange flesh - not a good look!
  • The inverse is true - if you are taking photos of a rock band with a light show, then you'll want to preserve the colour of the lighting and may not want to adjust light balance.
  • If you are taking photos of a sunset or sunrise, you might want to take a photo with a gray card so that you know what neutral lighting looks like. If you are adjusting white balance manually to taste, then it is nice to know the boundaries and neutral will be at one end of the spectrum. However, to emphasize Tim's point, neutralizing a sunrise makes the effort to get up in the morning pointless.
I hope this helps with this confusing topic.

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