Iliah Borg writes: Knowing that green is more sensitive, one of the tricks to equalize channels better while shooting with daylight/flash is to use a magenta filter, about 30 to 40 percent depending on the camera (CC30m, CC40m; P instead of m if the filters are from Germany). This will also improve colour reproduction if… [Read More]
Testing for ETTR, part 23
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]
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