Ever since I starting working in camera space, I’ve had what I needed for a true one-step UniWB calibration procedure, but I didn’t have a delivery mechanism, since the procedure required inverting a matrix, and I was using Matlab for that. I poked around and found that Excel can invert matrices, and multiply them too…. [Read More]
Testing for ETTR, part 22
Iliah Borg has pointed out that he does his UniWP calibration in a monitor space with native primaries and a gamma of one. Not using the native primaries might be one source of inter-channel crosstalk. To find out if this is significant on my NEC PA301W monitor with the D800E, I made three exposures at… [Read More]
Testing for ETTR, part 21
Now we have two methods for UniWB that work just fine. One, the gridded search, requires only Rawdigger and Photoshop, and doesn’t make the user do any math beyond adding and subtracting integers. Newton’s method comes in two flavors. The simple monitor space approach takes a while to converge, but works well. The matrix-based camera… [Read More]
Testing for ETTR, part 20
In a private communication, Iliah Borg, one of the early proponents of, and an expert on, UniWB wrote to me: “Suppose you are displaying some grey on your monitor, shoot it …and white-balance the shot. Now if in linear space you multiply the R and B by the resulting custom WB coeffs you should have… [Read More]
Testing for ETTR, part 19
I’ve figured out why I couldn’t get either the D4 or the D800E to white balance to the screen shots. It was pure cockpit error on my part. I misread the manuals for both cameras, which are virtually identical with respect to white balancing. I thought you could get the camera to compute and store… [Read More]
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