When Using Flash, Is AUTO White Balance (AWB) Really Used?

At the July 21, 2007 HAL-PC Clear Lake Digital Photography SIG meeting there were a couple of questions/issues of disagreement. This article covers one of them. If I find time I will prepare an article on the other later.

When using Flash with white balance set to AUTO, does the camera in fact not use the AUTO white balance after all, even thought it says in the EXIF that it did?

I wasn’t able to find a definitive answer to this question on the web. My guess is it isn’t stated because AUTO white balance is used when the EXIF data says it’s used, thus no one sees a need to post articles stating something that’s normal/as expected/as assumed.

Below is some of the little I’ve found on this. My indirect conclusion from these references leaves me assuming AUTO white balance is used with flash in the same way it is used with any other light source(s). An exception would be some cameras that have a special “Flash white balance.” A subset of these cameras switch to this mode when shooting Flash. The only cameras I know of that have Flash white balance are DSLRs, which most people don’t have. But, the very fact that they have a Flash white balance mode must mean it’s different from AUTO white balance. None of the five digital cameras I have owned have/had a Flash white balance mode. But, if one your camera has one and it is used, I assume (and hope) the EXIF data would say that, thus making it clear AUTO white balance was not used.

This article has examples of pictures shot under various modes. This camera used has a Flash mode and the images illustrate that the image shot in AUTO white balance have a different color balance than the one shot in Flash white balance.

This post says:

“There’s no doubt that all of the test photos shot on the Flash white balance setting (including mine, yours and Bruce’s) are off-color. And it’s also true that the photos shot on Auto white balance appear to be much better.” [emphasis added]

Again, this statement makes a clear distinction between shots made in AUTO white balance and those made in Flash white balance.

This article says:

“So, here I am on Auto WB and using flash. . . . because the D2x is functioning in a “mixed” lighting environment, it must deal with both types of light…the 5400K flash, and the 4200K fluorescent” [emphasis added]

The statement clearly suggests his Auto WB is taking into account all sources of light, not just the flash.

Again, this post says:

“Auto WB does a great job on my D70. Even when my SB-600 [flash unit] fires. I’m pretty sure the camera’s on-board computer calculates the optimum WB after the image is recorded. Which makes sense. I wouldn’t want it effectively fixed at the “Flash” temperature just because I have a flash unit attached. I may be shooting fill flash . . .”

Obviously, the confidence you can place in the above references is limited.

The following reasons leave me believing AUTO white balance works the same with flash or without.

  • the EXIF data says AUTO white balance was used
    in mixed lighting images using fill flash would not be properly balanced if not corrected AUTOmatically
  • the implications of above references
  • the absence of links to the contrary
  • my experience

If a camera is using Flash white balance, it is not using AUTO white balance, and I assume this is made clear in the EXIF data.

Someone suggested there were different meanings for AUTO white balance — one meaning when using flash, and an entirely different one at other times. I think this is unlikely.

I welcome any clear/unambiguous and authoritative references that will settle this question without having to read between the lines.

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