Red and Blue

by Gordon

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2

Interpolate the R and B numbers logarithmically. We perceive light intensity that way, not linearly. For example, the same scene taken at a sequence of decreasing f-stops with everything else held constant yields a sequence of pictures that look successively lighter, with each step feeling roughly constant. However, the actual amount of light will go in a ...


0

I've been experimenting with what seems to me like a practical method of fine-tuning, which is basically just "morphing" between two white balance settings, each of which is a "correct" setting for one of the lighting situations in a mixed light image. This seems like a nice way to nudge a single slider around, rather than juggling temperature and tint. For ...


0

Just because the paper is white does not necessarily mean that it appears to be white in the image. Your camera can only see the light that is reflected towards it. It's essentially the same "problem" that you have with measuring the amount of light to find the correct exposure. You never know if what you see is a bright object that is in low light, or a ...


0

Anyone favoring a Kodak 18% gray card should realize that Kodak sold that printing business 20 years ago. And it sold again after that. Last I heard, Tiffen is the current owner. The card may still say Kodak, but it is probably licensed out to a few no-name third parties. Be that as it may, an 18% gray card is NOT specified to have accurate neutral color. ...


-1

Settings in the camera (except exposure) do NOT affect the Raw data. Raw is raw. However, Nikon raw software has options to pull the settings from the Exif and apply them. Adobe raw software can pull the WB and use it as "AS SHOT" WB (but only WB). Probably the other software can do something, but I can't tell you what. So if you want Vivid, you set ...


0

Frankly, this does not sound practical or usable, but to do it, you can take a picture with your camera of each of Daylight and Shade WB, and then in manufacturers section of the EXIF, see like: WB_RB Levels: 1.82421875 1.5234375 1 1, which are the multipliers used for R, B, G, G. Each pixel of course. But WB settings (daylight, shade, etc) merely tell ...


1

If you find that hitting the "auto" button in the GIMP levels dialog generally does the thing you're looking for, you can batch that as described here. Specifically, you would put this script: (define (batch-auto-levels pattern) (let* ((filelist (cadr (file-glob pattern 1)))) (while (not (null? filelist)) (let* ((filename (car filelist)) ...


1

White balance is a very straight forward image processing manipulation. It's just a per channel gain in linear RGB space. JPG files are sub-optimal for doing white balance as they usually have both a tone curve and an inverse monitor EOTF applied breaking the linear relationship with the scene luminance values. This is why it's usually done starting with ...


2

I had a great picture of a lady I took under weird, complex lighting (sodium vapor and mercury vapor lights). Great smile, perfect focus, excellent picture except for way, way off color. I monkeyed with temp/tint for an hour in adobe Camera Raw with no good result. I wrote a program to hack the sidecar XMP file varying the temperature and then creating a ...


3

White balance is applied while processing raw data. The purpose of white balance is to reach R = G = B for neutral (grey, non-colored, achromatic) areas of the image. The whole problem arises from the fact that color channels of the sensors (for typical Bayer, those are R, G1, B, G2) have different "sensitivities", and the responses also depend on the ...



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