Canon 5D2 AWB and exposure

[Hening Bettermann]

When trying to exposure-stack some images taken with the Canon 5D2, I discovered that the AWB of the camera changes with exposure. Here is the result of a mini investigation, comparing to the Nikon D200.

"Ref" is an exposure where I try to hit the overall lightness of the scene, i.e. the middle tones. In the cases referred here, the ETTR was darker than this. +4EV is 4EV above the ETTR. Temperature and Tint are as displayed by Raw Developer on the linear image, shown with my camera profile (but this makes no difference).

Of the Canon images, the overexposed ones are closest to my memory (and to RD's "Daylight" WB, as can be seen). The underexposed (ETTR) ones are grossly red. The Canon AWB seems to have the built-in concept "The darker the image, the more rosyfying it needs".

Good light, and ACCURATE colors! - Hening.

[Rhossydd]

Not seeing that issue here with my 5Dii. Going back and looking at my bracketed shots in LR the 'as shot' colour balance stays exactly the same for each three shots, +2,0-2

[Hening Bettermann]

Hi Rhossydd,

thanks for your reply.

Uff, now I recall that the Canon had firmware failures at the time the images were shot an has been updated since.
So now I did a little test in my living room, with energy saving lamps.

Impression: the AWB is accurate UP TO an exposure that gives approximately correct mid-tones.

[madmanchan]

It depends on the scene. For example, when I tried manually bracketing while photographing a sunrise (not auto bracketing), I got very different readings for the different exposures (anywhere from low 3000 K to low 4000 K).

[Hening Bettermann]

Hi Eric,

thanks for your comment. - I remember vaguely having read that the Canon does not white balance correctly either when the gross overexposure method is used. So it seems that the only way is white balancing by memory while the memory is fresh.

Good light - and ACCURATE colors - Hening.