Me neither! I’ve since tried it on about 20 images and found it is not necessarily more (subjectively) pleasing every time, but what I’m most interested in trying to work out is whether it produces more accurate colour.
Sum of adjustments = 1 so greys stay grey. Other values were chosen to produce natural colours in combination with the IR profile. I arrived at these values working on another image with greater variety of hues. I began by swapping R and B channels, which returns normal hues when doing infrared things, but the image looked very desaturated, especially green. Thus I boosted saturation of G in G channel, summing to 1 by reducing R and B equally. But the greens still looked washed out. Reducing them in R and B channel helped that, balanced by increasing B in R, and R in B. This gave everything a similar saturation to using 3x3 matrix, and correct hue (I think), though since posting I discovered it to over saturated greens, so made some slight adjustments.
Yes, although I still haven’t decided yet. Partly because I don’t really know why it works!
Here is the hummingbird playraw example. Only other colour adjusting modules used are white balance and filmic. All modules are exactly the same in both versions, except as listed below. Pipe order: Ch mix placed before Input Profile, placed before exposure. Used darktable 3.2.1.
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Input: L IR, Ch Mix on
_MG_0113.CR2.xmp (63.8 KB) -
Input: 3x3, Ch Mix off
_MG_0113.CR2_01.xmp (65.4 KB)
In the original thread there was discussion about what colour the flowers ought to be. It was decided they were more blue than violet. (Link to the example he linked to: Salvia x 'Big Swing' - Big Swing Hybrid Sage) Yet we can see, using the standard 3x3 matrix and not shifting hue in any other module (except white balance), they appear more violet. In the IR + Ch Mix version, they appear the correct blue, AND have nicer tonal gradients in the highly saturated areas. [The reds appear the same. The greens in IR+Ch Mix version are yellower - I don’t know if that is accurate or not. Did I just get lucky once or twice, or is this the way to go every time?]
Here is the Erlaufschlucht playraw:
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Input: L IR, Ch Mix on
P9120141.orf.xmp (70.0 KB) -
Input: 3x3, Ch Mix off
P9120141.orf_01.xmp (71.6 KB)
Hues are similar, but first has an increase in saturation. It looks more natural to my eyes, but I wasn’t there. @betazoid might have an opinion? I’d be interested for people to try it on their own images and report back whether it looks more natural, and how reliable it can be for a variety of different cameras.
New ch mix values:
Red channel
R: 0
G: -0.75
B: 1.75
Green channel
R: -0.25
G: 1.5
B: -0.25
Blue channel
R: 1.75
G: -0.75
B: 0