RAW vs White balance

Started Nov 20, 2006 | Discussions thread
GordonBGood Veteran Member • Posts: 6,308
Re: Manual WB does impact *istD RAW

edhannon wrote:

You were right. The first curve below was with a manual WB shot at
a deep red chair. The second shot with a light blue folder cover.

So, it looks like the *istD does not change the raw values in the
preset WB modes but does in the manual mode.

Ed, I think that if you check your results carefully, that the R/G and B/G ratios are changing, but more slightly - something in the order of 25%.

However, I notice that it does not do what I had hoped it would -
that is extend the DR. The highlights of at least one color still
saturate at about 3 stops above meter reading (EV = 8). In fact
with the light blue card I lost 1/2 stop.

The curves look as though you might find a color of card that would
extend the highlights by about 1/2 stop. But not worth the effort
in my opinion.

Of course you don't extend the DR much because the green channel gain is left untouched; all the camera does is change the relative gain of the red and blue channels to optimize for the requested wb setting. In the case of wb presets and especially Manual WB, this effectively reduces the gain of the strongest channel to avoid that channel clipping sooner than expected, resulting in slight extra exposure headroom.

You may be interested in vortout's other thread related to the K10D, somewhat related to this one at:

http://forums.dpreview.com/forums/read.asp?forum=1036&message=21236953

Regards, GordonBGood

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