Two Infinities

Wed, 27 Jun 2007

Trying to get colors right in photography
Over the last couple of years or so, there have been a number of fabric colors that I just never seem to capture. Today I just want to make a note of my attempts to reproduce the olive green that some of my military web belts exhibit.

First step: setting the white balance on my camera. I have a Nikon D-50, and I set the white balance by photographing an 18% gray card.

Second step: including a color checker in the photograph of the fabric:

In this photograph, exposure was chosen that seemed best to reproduce the color checker as a whole. Also, the grays correspond pretty well to the values for sRGB at brucelindbloom.com. My 2 high and low values are spot on and the middle two are high by 13 (out of 256). Measurements of the image of the color checker were taken with GIMP's color picker.

My own problem with this photo is that it seems to change the olive drab to a brown drab. The problem can be seen in the color checker in the first spot; the "dark skin" or "moderate brown" have listed sRGB value of (115, 80, 64) while the photograph above reads (139, 77, 57). There is too much red in the medium brown. Using GIMP's color curves to tone the red down around the value of the olive green in the belt does improve the color reproduction of the olive green--but, of course, throws the greys out of whack.

It is also curious to me that the other related color, "foliage" or "moderate olive green" is pretty much in line; (88, 113, 64) in the photo and (88, 108, 65) in the chart.

I can only conclude the problem is in the camera (or the camera software).

posted at: 23:47 | path: | permanent link to this entry