RawDigger also allows me the functionality of exporting the each individual channels of the Bayer array image as a separate tiff, with the pixels for the other channels zeroed. RawDigger also has a tooltip readout of the pixel intensities in the raw image, which suggest that the two greens have approximately the same intensities, the red has intensity about 50% more and the blue has 40% less. Hoping to get to the bottom of this, I went searching for software that will let me read out the honest raw sensor values, and I found the shareware RawDigger which offers a 30 day free trial, which very nicely lets me pull out the non-demosaiced separate channels in the Bayer array of the raw image, which it denotes R, G, B, G2.-there are two green channels, reflecting that every 2x2 block in the Bayer array has one red, two green and one blue pixel. Now it seems that the blue channel has the smallest intensity, the green is intermediate and the red is the brightest. However when I toggle the raw histogram button as pictured here,a different story is told. Note that the green histogram indicates a much less bright intensity distribution that the blue, which is less than the red-which nicely sums up the color of the image. Raw Therapee also gives me the histograms associated with this image, a screen shot of this is below. When I open this image in Raw Therapee, with the white balance setting as "Camera" I get the standard IR-ish pink-purple image I took a photo of weeds and dirt road (lots of that around here) using my canon sd1100, with the hot filter replaced with a life pixel standard ir filter, running CHDK, and saved as DNG. These are specifications are no longer valid when using the camera for NIR imaging, and with a little reverse engineering we might be able to re-imagine the low level image processing to better suit our needs. I am interested in something a different-the camera ccd sensor, the Bayer array, and the camera or digital negative development software white balance settings were all designed by some smart engineers who assume certain specifications about the sensor, the illumination and the relationship between the two. This paper is very informative, and also validates my own thinking on the subject, which ought to be worth a free beer.Ī natural photo-processing technique for making an image with good color contrast is to adjust the white balance, which I understand as a simple digital scaling of the brightness in the different color channels. Ned Hornung's post last September had a pay-walled link to a nice academic paper with an NIR spectral characterization of digital cameras, this link seems to be a free version. This post is a data-dump of what I've learned and what I'm thinking. Along the lines of Chris Fastie's post last September, I've been wondering what real spectral information is in the color channels of an ir-converted point and shoot camera.
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