Rob Studdert wrote:
On 28 Dec 2005 at 14:56, Gonz wrote:
Isnt RAW supposed to contain "raw" RGB data? If any of the individual
pixel sites, R G or B maxes out, it would be useful data. Maybe I dont
care about blowing certain channels (pre-bayer). I know that final RGB
data is a Bayer combination of the RAW data, but the RAW data is still
quite useful. I suspect, but cannot prove without some emperical data
that you will probably find that the pre-bayer and post-bayer RGB
histograms are pretty similar.
Unfortunately the in camera histogram of a RAW file is derived from the jpeg
file embedded in it which is in turn affected by both the in camera colour
balance and the contrast settings. So the histograms will only be similar in
camera and post-bayer if the image is decoded with a similar colour balance, un
adjusted levels/exposure and contrast settings.
Correct, thats the way its done (histogram from jpg). You would have to
have the white balance setting close to actual. But there's no reason
why they cant take an RBG histogram direct from the raw data. A simple
non-bayer filter-like transformation would all that would be needed to
get a white balance accurate histogram, no?
I guess the lesson in all this is that even if you are only using RAW,
you should still set the white balance, at least for the sake of an
accurate histogram.
Rob Studdert
HURSTVILLE AUSTRALIA
Tel +61-2-9554-4110
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Pentax user since 1986, PDMLer since 1998
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