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That is called "white balance", not "white point"
Authored by: elmimmo on Feb 11, '05 11:59:12AM

Technically, white/black point correction is a completely different thing (ie, turning the brightest/darkest levels in your photos to perfect white/black). This is, technically speaking, exactly called White Balance correction, which tries to correct the tint that the dominant light is sheding (warm orange for a bulb, greenish for fluorescent) or Color Temperature, which your eyes usually adapt to, and hence you do not see with the naked eye. When trying to correct Color Temperature you should point a pixel which does not have any color channel at 255 o 0 values (max o min values), you should rather point a pixel which you think should be grey between mid gray and full white instead of yellowish of blueish. If you choose a full white one, iPhoto cannot compare how each channel is biased from another and thus chooses a default (high) color temperature, which is NOT what you want.

This way of correcting photos is actually commonly done professionally, provided that you carry a small card which is proven 100% perfect neutral gray. That way you photograph the card in the same context as you will make the rest of your photos, correct that photo later on, and apply the same correction to the rest of the photos which do not have a neutral gray card photographed.

Rob, you should change the title of the hint to read something like "Set White Balance correction in iPhoto 5 with point and click".

PS: I actually just implied this from the hint's text, since I do not have iPhoto 5 ^_^



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That is called "white balance", not "white point"
Authored by: elmimmo on Feb 11, '05 12:11:12PM

To those new to this "white balance" concept, here http://www.whibal.com they sell a "neutral gray card", and there you can see how and what one of those is for, and how it is used in professional photo editing software. Usually you can only accurately correct white balance on photographs in RAW format, not JPEG or other. I do not know about what iPhoto 5 does or how accurate its corrections are, though, since as I said, I do not have it.

You can see a live demo of its use at http://rawworkflow.com/WhiBalManual/index.html

I am not related to that guy in any way, BTW.



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