Help with Adjusting White Balance using Curves


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Jun 18, 2005
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#1
Recently I've read online on how to adjust the colour balance of pictures using curves to obtain a correct white balance. It said to set a white/grey/black point.

Now using my common sense, I select a pure white/blown out area of the picture to set as my white point, there wouldn't be, and there isn't any, change in the white balance of the picture.

So does it mean that I only select what I THINK should be white to set as the white point?

Thanks alot and pardon me for my noob question.
 

deathwiz

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Aug 2, 2007
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#2
You set your white point to be a point on the picture which is supposed to be white under normal conditions.

Example:

Under tungsten that point would appear orange, but if you select that point as your white point, the photo will be corrected with respect to that point as if that point was white.

If under tungsten you set a white (over exposed) point as your white point, there is no correction done as white is already white. :)
 

catchlights

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Sep 27, 2004
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#3
the overblown area is already 255, 255, 255, can't provide info to do any correction.

anyway, you should use the gray point for this, white point is for setting highlight, black point is for setting shadows.
 

Oct 23, 2006
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#4
if really the above doesn't work, use the black point and then manually correct colour balance.
 

jssales

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Oct 14, 2006
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www.pbase.com
#5
Recently I've read online on how to adjust the colour balance of pictures using curves to obtain a correct white balance. It said to set a white/grey/black point.

Now using my common sense, I select a pure white/blown out area of the picture to set as my white point, there wouldn't be, and there isn't any, change in the white balance of the picture.

So does it mean that I only select what I THINK should be white to set as the white point?

Thanks alot and pardon me for my noob question.
I’m assuming you’re using Photoshop for correcting your white balance?

As mentioned in an earlier response, using specular highlights as your white point is not advisable as there is no detail in that area. You’re looking for an area of white with detail, just as a black point is ideally not pure black but with a little detail.

Here’s one approach – create a threshold layer. Your image’s pixels should now be either black or white. Move your slider all the way to the right and your entire image should now be black. Slowly move your slider to the left until a you see a few clusters of white appear. That area is your image’s white point. You can now define that using curves or levels.

To capture more detail, I usually clip my output levels to 4 and 251 instead of 0 and 255.

And unless your monitor is calibrated and your environment is free from color contamination, color correcting manually won't be spot on.

Hope this helps.
 

Apr 4, 2007
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#6
you may just wanna try to auto level. it works most of the time (for me). :thumbsup:
 

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