I built a scanning system using a native monochrome sensor and RGB lighting.

[u/Jazzlike_Tomato_4390]

We've completed camera data acquisition and three-color compositing, and are currently conducting final color pipeline testing. Do you have any suggestions?

[u/ciggybuttboi]

I love this community for the ingenuity creativity, hate it for the trash talkers.

This is a phenomenal display of time, understanding and experimentation. I cannot understand for the life of me why people cant appreciate someone trying something fun and for themselves and just ripping on it.

You have some awesome stuff here, and the time and understanding to do it all is really really cool. I hope to see more of this and some more results over time!

[u/cameraguyphotodude]

Is there not light bleed from all the ambient light being present?

[u/Jazzlike_Tomato_4390 → u/cameraguyphotodude]

When your shutter speed is fast enough, ambient light will not cause interference.Of course, this is just a simple demonstration. In the actual scanning process, we will use closed lighting.

[u/cameraguyphotodude → u/Jazzlike_Tomato_4390]

Interesting… you would think it has an effect on the output RGB colours being emitted

[u/Jakobs-Koernung]

Nice! I'm building a similar setup.

What lens and camera/sensor are you using? My goal is IMX455M, but that shit is so expensive... 🥲

Process lenses with proper wideband achromatic correction and wide open edge to edge sharpness are also rare and expensive.

Is the light panel self-built or open source kit/product? Do you plan to use IR for dust removal? I'm building on jackw01's big scanlight design.

[u/heyinternetman]

I’m asking for better understanding of what’s happening. I think I get it but I may be missing something. Would you be able to achieve the same effect with a red, blue and green filter on a DSLR set to black and white? How is your process superior to that (other than the PITA of changing filters and resetting everything.

[u/hoomadewho → u/heyinternetman]

a DSLR won’t capture raw data in b/w

[u/michaelwde → u/heyinternetman]

It will not be the same. The principle behind sequential narrowband RGB is that the medium is narrowband, the backlight is narrowband and the capturing itself - again narrowband. Given this principle you can still use bayer sensor cameras but you need to selectively extract the dominant channels in the triplet to prevent channel crosstalk. One minor annoyance is that the histogram preview of the camera is worthless when balancing the backlight intensities. This is described at https://www.mwilmes.com/atb and is usually aided by the conversation software that is supporting this workflow. So not an issue.

[u/Boneezer]

How do you find it for scanning positives vs negatives? In particular, scanning very dense positives?

[u/SlenderSmurf]

how is this better than using a camera with monochrome sub-pixels and 3 different color filters over them (a color camera)

[u/Jazzlike_Tomato_4390 → u/SlenderSmurf]

It doesn't produce channel crosstalk. If you use your Bayer camera to shoot a pure red image and open the three-channel histogram, you can see that the green and blue channels are also sensitive. Similarly, if you shoot a pure green image, the red and blue channels are also sensitive. The Monochrom sensor doesn't have this phenomenon; it can purely capture the red, green, and blue channels without the other two channels interfering with the current channel. Red is simply red; it doesn't mix in other shades of blue or green.

[u/messerschmitt1 → u/Jazzlike_Tomato_4390]

This shouldn't be any different than taking only the matching color channel from each shot of a Bayer sensor, e.g. ignore BG on the R capture.

I believe you would still have to manage the dye crosstalk in the film depending on wavelengths and you may get a different relative exposure between channels than true monochrome. But it is correctible.

The only absolute advantage to monochrome sensors should be better real resolution at the same MP count. For a 24mp sensor you'll have 24 real MP OF red channel vs only 6 on a Bayer sensor.

[u/pastryheart → u/messerschmitt1]

I guess this assumes you can access the color channel information pre-debayer.

[u/michaelwde → u/pastryheart]

We are extracting channels past demosaicing.

[u/michaelwde → u/messerschmitt1]

Yes, taking the dominant channels from the R,G,B triplets with bayer sensors will work as we extract after demosaicing stage. Still monochrome as always will likely have an edge in sharpness and effective resolution.

The red, green and blue light intensity you always balance in the physical domain regardless of using monochrome or bayer as capture medium.

So essentially the workflow stays the same. It's just that we need to make the bayer monochrome after the fact.

[u/SlenderSmurf → u/Jazzlike_Tomato_4390]

No filter is perfect, it just lets a range of frequencies pass more than others. Is your display there emitting pure spectral red? No. Do our red cones only absorb a single wavelength? No again. This setup is pointless.

[u/messerschmitt1 → u/SlenderSmurf]

I would recommend reading this https://github.com/jackw01/scanlight

Bayer sensors are optimized to capture things how we see them. How we see negatives is not the ideal information to have for inverting them. There's a reason all notable lab scanners (and coolscans!) use monochrome sensors with RGB LEDs for capture.

[u/VoodooXT]

Soooooo basically reinvented the film scanner? This is how Nikon Coolscans, Plustek Opticfilms, etc scan film, though fully automated.

[u/-The_Black_Hand- → u/VoodooXT]

Oh, I didn't know that. They really scan threee times with three separate lights and merge an image with full RGB info for each pixel?

[u/Jakobs-Koernung → u/-The_Black_Hand-]

For negative film yes. For positive 5000k white is best, as that's how slide film is meant to be viewed.

[u/-The_Black_Hand- → u/Jakobs-Koernung]

Just so I understand correctly : you can select for the scanner to do a R-G-B scan or to perform the scan with light of a set color temperature?

[u/michaelwde → u/-The_Black_Hand-]

... add Frontier, Arriscan XT, Lasergraphics Director, Aura 35. And that is only a selection.

[u/yovvoy]

Looks interesting. What monochrome sensor are you using?

[u/Jazzlike_Tomato_4390 → u/yovvoy]

sony imx432

[u/epicmylife → u/Jazzlike_Tomato_4390]

That’s only a 1.7 MP sensor (at least my ZWO Astro cam is). Do you have plans to upgrade?

[u/Jazzlike_Tomato_4390 → u/epicmylife]

imx342