white balance without white ?

ulisses

ulisses

Well-known member
Hello !

In the last 15 years, I always used a white reference to set the white balance. Now with the PD's DVX's I found the camera being able to set the white balance even in a full image with many colors on it.
I'm curious to know how PD, DVX, etc can adjust the white without the white :) I know the correct is using white but I saw good results in white balance without white as well.

Thanks,
Ulisses
 
AWB tracking in digital cams is based on the analyisis of low saturation area's in the image. The area's where the chroma/luma ratio is below a given threshold are summed up and a feedback system corrects them to zero ("=native camera white) If there are no low saturation area's, the cam keeps the fixed(native) white, which can be subjectively looking wrong after scene changes.
 
thanks for the explanation andre, makes sense. Anyway I think the camera shouldn't adjust the white balance in A or B if white isn't supplied and AWB is off.

Ulisses
 
Errmmm... the camera doesn't adjust the balance by itself with AWB turned off. A and B are just presets and the camera could care less if white isn't supplied, it adjusts to what you tell it is white.
 
Yes, but if I set to A and click the button to set the white balance, even without white it finishes the balance, from my experience other cameras couldn't set the white balance without a correct exposed white reference.

Ulisses
 
ulisses said:
Yes, but if I set to A and click the button to set the white balance, even without white it finishes the balance, from my experience other cameras couldn't set the white balance without a correct exposed white reference.
Click to expand...

That's absolutely wrong. You can hold up a red card and take a white balance with any camera. The camera will think that the color red is actually white.

Just think about it. If you're indoors using incandescent light, the white card actually looks yellow/orange (color temp 3200k). But yet you can tell the camera to calibrate this as white.
 
You could point the DVX at a street scene and hit "white balance", and it'll come up with a pretty good guess as to what should be correct. It doesn't need a full screen of white, it just "knows" -- as do many other cameras. You can ensure better results if you provide a white card, of course -- just as you can "fool" the camera by giving it red (or other) cards to fill the screen.
 
Yes Sumfun and Barry... you are correct, I couldn't get white balance with wrong expusure and not wrong white, I remember using different parts of a white wall to get a desired color temperature (in cameras without K adjust). In DVX it can be done using the color settings in menu :)

Thanks,
Ulisses
 
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