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Comment by goblin89 | Hacker News Reader

I wonder if there are ways to get superior (compared to Bayer) color images from conventional raw-capable monochrome digital cameras (like Leica Q2 Monochrom) in static scenes using similar workflows of taking three separate shots.

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Many cameras, especially medium format like Fuji GFX, can do "pixel shift" capture, where they use the sensor stabilization to shift the sensor by one pixel at a time to ensure red, green, and blue are each captured at all pixels, without needing demosaicing. The camera has to be mounted on a tripod for this to work - like any stacking requires, really.

Initially I thought pixel shift might be the way to go, but stumbling across [0] I got an impression it isn’t necessarily as great as it sounds (and, I guess, neither would be any three-shot RGB-filter-swapping composite).

[0] https://www.dearsusan.net/2020/11/09/nyquist-mtf-pixel-shift...

Absolutely! [0]

In fact, the first color photos in the world were taken this way in the early 1900s [1]: take three monochrome exposures onto black and white transparencies with R/G/B filters, and then project the three images together.

[0] https://leicarumors.com/2020/01/29/color-photography-with-th...

[1] https://en.m.wikipedia.org/wiki/Sergey_Prokudin-Gorsky

Interesting. Sadly, I believe the Photoshop approach would not produce a DNG file that you could normally interpret in a raw processor of your choice. Looks like pixel shift cameras (which apparently still use Bayer sensors, just moving them around, to debayer at capture time so to speak) is the most practical option at the moment.

I’m curious if it is technically possible for a digital sensor to capture the entire light spectrum of the scene, without the need for RGB separation at any stage—similar to Lippmann plate[0].

[0] https://en.m.wikipedia.org/wiki/Lippmann_plate

There are Sigma cameras with a Foveon sensor that can do it:

https://en.wikipedia.org/wiki/Foveon_X3_sensor

Though they're not as good in most other dimensions as conventional Bayer filter sensors (most Amazon reviews e.g. say that it's impossible to photograph moving human subjects without daylight iirc).

I looked at Foveon before, and got the impression that it still effectively relies on RGB separation/recombination, though in a more elegant way than Bayer sensors. (That said, Sigma’s doing some really cool stuff.)

Sergey Prokudin-Gorsky‘s work shows both the benefits and drawbacks of the swapping filters approach

[1909]

It's standard when using reflectic/catadioptic objectives to peek back at where the satellites are: https://www.astroshop.eu/filter-wheels-filter-sliders/starli... This one has USB, the same style with manual operation via a teethed wheel is like 169 EUR at that shop. Or consider rigging a burnt-out DLP projector's filter wheel up, which comes with a motor and encoder that you could use to capture imagery with the filters they provide at much higher frame rates (a few hundred fps in the monochrome domain seem usual these days, AFAIK, for good consumer DLP projectors).

Love both ideas…

The first imaging driver that I wrote was for an HD frame store that had a camera with a spinning filter disk.

That sounds very interesting. I feel like firmware/hardware automation combo that swaps RGB filters and takes exposures in accord could provide interesting workflows for owners of those monochrome digital cameras.

I wouldn't be surprised if these military bombing dudes not only took R, G, B, but also near IR, far IR, UV, and various other things. If they did it would make no sense to try to make a Bayer filter for all of that and rather just have multiple filtered cameras pointed at the same direction.

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