Hello,
I need to edit photos of an artist’s work. Only with the WB I have due difficulties, because unfortunately he had used an AWB.
How do you do a manual white balance when you don’t have a neutral white or black in the image?
Automatic white balance sometimes gives good results, sometimes useless. So I have to go ahead manually.
Unfortunately, the paper tone is not a neutral white, but rather a cream white color. But it is important that all pictures get the same tone for the paper and the passe-partout.
Is there a way to transfer a specific tone, from the paper in the passe-partout, for example, from one successfully processed image to another?
Hello
that sounds very interesting. The first 3 steps were easy to follow.
But then:
4. where did you get this “color sampled” from? Did you take it out of a well processed image? And why does an image in Mode: Multiply take on this color? Very exciting but still fully mysterious for me.
Other cameras would have put their “computed” color temperature in the Exif (unfortunately not the case here), so you could use that as a starting point in Colors > Color temperature, the other slider being either eyeballed, or set to some estimate of the actual color temperature of the light source.
Btw, there is a slight reddish cast at the bottom of the passe-partout, also visible in the "good " one.
Very amazing what is possible there. And the content of Pat Davis’ tutorial is absolutely logical and easy to follow.
The effort to execute it is huge if you want to do it perfectly. But with the two color pickers is well doable. I don’t have to match all the tones perfectly.
Your contribution and that of Pat has expanded my knowledge well.
The color cast at the bottom is from daylight illumination when taking the photo. I think you can live with it.
Maybe it would have been better if I had just asked a question first:
How do you do a manual white balance when you don’t have reliable gray or white values?
I do it with the curves: There I adjust the values for R, G and B so that the curve starts just before the black mountains and ends a little after the white ones. This works quite well.
I turn off the upper layer and apply the white balance with levels to the lower layer. I can either do this automatically or use three color pickers for shadows, middle gray and highlights:
Hello @s7habo
Great!! The Layers idea is the solution to this problem. Pretty simple in principle, easy to follow and very effective.
Thanks a million, Boris.
If you switch on the “logarythmic histogram” (at color levels or color curves), you can see much more precisely the values (the amount of pixels at the beginning and at the end of the scale). Why don’t you always use this setting? And, isn’t this setting much better for white balance?
The difference in the display is so huge: When is which setting useful?
Hello @ggbutcher
No, unfortunately my friend took the photos in changing daylight. The color of the mounts is always the same, so I can go by that.
If I edit the photos further, he will bring me an original. Possibly I will re-shoot it with white balance and then have a reference.
Of course I could re-photograph all 10 pictures for him, but it is also interesting for me to learn how to solve such a problem with Gimp.
But there is a big difference in the display whether logarithmic or linear. With logarithmic, I can see much more clearly where the “mountains” of the light distribution are than with linear. And when I manually adjust the white balance, it makes a significant difference. The linear histogram seems to understate the extremes.
My question is: when to use logarithmic and when linear display of the histogram?
