Re: Need help interpreting color test results


Johan W. Elzenga wrote:
ronviers@xxxxxxxxx <ronviers@xxxxxxxxx> wrote:


With all respect; you sound like somebody who tries to fly by lifting
himself up. People tell you that will never work, but you continue to
try saying "I may not understand gravity, but I can be very thick
headed". Yes, apparently. But that still won't make you fly.


--

Johan please do not get aggravated with me; I cannot help how I am. I
mentioned earlier in the thread that it does not need to come to
something.

I realized that all I need to do to get neutral data into the camera is
to either fully saturate the sensor or completely deplete it. So I
first took a picture at 1/4000 of a second with aperture closed and
lens cap on at ISO 100. I know that all sounds redundant but I tried
other settings with the lens cap on and those settings gave me the
skinniest (most dark) histogram. Then I took another picture while
holding the camera directly at a light with a 30 sec exposure. All the
histogram flashed so I knew it was full. Then I used the black (fully
depleted) image as the source file for wb. Then I took a picture of a
backdrop with a blue cast. This gave me an image of R=76,G=117,B=58.
Then I took the same picture with the white (fully saturated) image as
the source for wb and got R=77,G=117,B=59. Consistency! Now all I have
to do is create an image in CS2 with the color ratio of something like
R=131,G=100,B=159 to cancel out the green then I should have a truly
white subject to photograph so I can remix my paints and get rid of the
blue cast on the original backdrop. So my question is, can anyone
explain why, if I use either the depleted or saturated image as a
source for wb the resulting image is so green? And remember it is
green even though I am photographing a subject that has a blue cast.
Btw, green does not bother me as long I can count on those ratios.

I give up. I've tried to explain to you what a custom white balance
does, but I failed.


--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl

One of the first tests I did with my camera was to photograph a
backdrop lighted at the top with tungsten and at the bottom with
fluorescent. Then used that image as a source for custom wb then shot
the image again. I learned that, at least with my camera, there is not
a pixel by pixel neutralization of white. I could get one of the
whites neutral but not both. It was not all bad though because after
balancing one color it left me with a gradient that I could use in PS
to balance the other white.

Brgds,
Ron

.

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