3 Replies Latest reply on Jun 27, 2008 2:26 PM by MadManChan2000

    WB Temp/Tint values - how accurate?

      I wonder where do these values come from? For example, I have a Canon 30D, and I've made a series of shots if the same scene with Auto WB. Now, ACR tells me that some of the photos have slightly different WB values. Supposedly the lighting conditions have changed. So, do these values represent actual colour temperature (being, perhaps, readings from some sort of colorimeter built in 30D), which means that I can safely level them across one shoot to get constant colour, or are they merely ARC's guess at the real colour temperature, which can as easily be wrong as a camera's Auto WB evaluation?
        • 1. Re: WB Temp/Tint values - how accurate?
          MadManChan2000 Adobe Employee
          The reported numbers are changing because the camera's internal "auto WB" algorithm is computing different WB results for your different images. The camera tries to estimate the WB using its sensor (or analysis of the scene) but it's only an estimate and as you point your camera in various directions the estimates will change even if the lighting is the same.
          • 2. Re: WB Temp/Tint values - how accurate?
            Elenhil Level 1
            So, at least, are these numbers derived directly from the camera's own WB evaluation, or they are a secondary evaluation on behalf of ACR? I suppose it depends on how much Adobe knows about a certain camera's RAW format, so I've mentioned my model.
            • 3. Re: WB Temp/Tint values - how accurate?
              MadManChan2000 Adobe Employee
              The numbers depend on the camera profile. CR uses different profiles than Canon's own profiles, so the numbers won't match, say, Canon's software (DPP).

              But your original question is about why the numbers are changing from image to image, and this is because of the camera's Auto WB feature reporting different values.

              If you set a manual fixed WB in the camera (e.g., switch your WB setting from Auto to Daylight or something that is constant) then shoot a bunch of images in a row using that setting, the WB numbers reported in CR will be the same for those images.