this post was submitted on 29 Dec 2025
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Good read. Funny how I always thought the sensor read rgb, instead of simple light levels in a filter pattern.
wild how far technology has marched on and yet we're still essentially using the same basic idea behind technicolor. but hey, if it works!
Even the human eye basically follows the same principle. We have 3 types of cones, each sensitive to different portions of wavelength, and our visual cortex combines each cone cell's single-dimensional inputs representing the intensity of light hitting that cell in its sensitivity range, from both eyes, plus the information from the color-blind rods, into a seamless single image.
You could see the little 2x2 blocks as a pixel and call it RGGB. It's done like this because our eyes are so much more sensitive to the middle wavelengths, our red and blue cones can detect some green too. So those details are much more important.
A similar thing is done in jpeg, the green channel always has the most information.
For a while the best/fanciest digital cameras had three CCDs, one for each RGB color channel. I'm not sure if that's still the case or if the color filter process is now good enough to replace it.
There are some sensors that have each color stacked vertically instead of using a Bayer filter. Don’t think they’re popular because the low light performance is worse.
This was sold by Foveon, which had some interesting differences. The sensors were layered which, among other things, meant that the optical effect of moire patterns didn't occur on them.
Some Sony phones have that type of sensor
At least for astronomy, you just have one sensor (they’re all CMOS nowadays) and rotate out the RGB filters in front of it.
Is that the case for big ground and space telescopes too? I can imagine this could cause wobbling.
Btw is that also how infrared and x-ray telescopes work as well?
It sure is! The monochrome sensors are also great for narrowband imaging, where the filters let through one specific wavelength of light (like hydrogen alpha) which lets you do false color imaging.
IR is basically the same. Here’s the page on JWST’s filters. No clue about xray scopes, but IIRC they don’t use any kind of traditional CMOS or CCD sensor.
3chip cmos sensors are about 20-25 years out of date technology. Mosaic pattern sensors have eclipsed them on most imaging metrics.