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A smartphone camera, DSLR or other camera does not work any differently though. It's just that an array of color filters is fixed above the sensor's pixels whic

A smartphone camera, DSLR or other camera does not work any differently though. It's just that an array of color filters is fixed above the sensor's pixels which would also be monochrome if it were not there. The readout of these pixels is automatically converted to a color image then, or stored as RAW for later processing. This color filter array is called a "Bayer filter". https://en.wikipedia.org/wiki/Bayer_filter https://en.wikipedia.org/wiki/Bayer_filter

qayxc 5y ago
I'd say there's still a difference in that while DSLRs and smartphone sensors have individual readouts for each colour channel, scientific instruments do not. So a DSLR or smartphone camera still outputs a multichannel image with a single sensor while scientific instruments are strictly monochrome. They don't take multi-channel pictures in a single shot and each full image represents a single channel. HST for example has three cameras - one per channel - while the MER cameras have a single sensor with multiple filters.
- _Microft 5y ago
  From what I know sensors do not have different readouts for the different color channels. All pixels are read out the same way and, with knowledge of the pattern of the Bayer filter in use, are then processed ("de-mosaiced") into a color image. If one removed the Bayer filter from a sensor (as difficult as that is) and skipped demosaicing while processing the image, one would end up with a monochrome image just fine. Using physical color filters for different channels and taking the same scene for each of them, one could create a single color image with even better resolution than the camera normally would. Why better? - this might disappoint you now! - consumer cameras count each differently colored 'sub'pixel as a full pixel. So half of the "megapixels" of your camera are e.g. green and just a quarter of them each red and blue (that's a common ratio for the colors). The camera then 'fakes' having a full set of RGB pixels by demosaicing, see https://en.wikipedia.org/wiki/Demosaicing https://en.wikipedia.org/wiki/Demosaicing ). Taking monochrome image with physical color filters would allow to use the full resolution of the camera for each color channel.
  - qayxc 5y ago
    That's exactly what I wrote, though. > From what I know sensors do not have different readouts for the different color channels. You know wrong then. HST uses three camera sensors precisely to have three different filters at the same time and at full resolution: https://www.stsci.edu/hst/instrumentation/legacy/wfpc2 https://www.stsci.edu/hst/instrumentation/legacy/wfpc2 So yes, the WF/PC2 does indeed have different readouts per channels because each channel has its own dedicated sensor. Maybe you simply misinterpreted what I wrote. The fact of the matter is that consumer level sensors return multi-channel images (the sub-pixel filtering is an irrelevant technical detail), while scientific instruments use dedicated sensors per channel. edit: just to clarify even further - there are no subpixel shenanigans with scientific instruments for both higher precision and to avoid cross-talk between frequency bands; hence separate sensors per frequency filter. if you want multiple channels at once (e.g. space telescopes), you therefore need multiple sensors as opposed subpixel filtering.
    - _Microft 5y ago
      OK, I think I understand the confusion now. I understood "readout" as hardware implementation detail (think: "readout circuit") while it seems to refer to the data of a particular channel, right? My lack of familiarity with the lingo seems to blame then. That "subpixel shenanigans" on scientific apparatuses are inacceptable should be understood.

qayxc 5y ago

I'd say there's still a difference in that while DSLRs and smartphone sensors have individual readouts for each colour channel, scientific instruments do not. So a DSLR or smartphone camera still outputs a multichannel image with a single sensor while scientific instruments are strictly monochrome. They don't take multi-channel pictures in a single shot and each full image represents a single channel. HST for example has three cameras - one per channel - while the MER cameras have a single sensor with multiple filters.

_Microft 5y ago
From what I know sensors do not have different readouts for the different color channels. All pixels are read out the same way and, with knowledge of the pattern of the Bayer filter in use, are then processed ("de-mosaiced") into a color image. If one removed the Bayer filter from a sensor (as difficult as that is) and skipped demosaicing while processing the image, one would end up with a monochrome image just fine. Using physical color filters for different channels and taking the same scene for each of them, one could create a single color image with even better resolution than the camera normally would. Why better? - this might disappoint you now! - consumer cameras count each differently colored 'sub'pixel as a full pixel. So half of the "megapixels" of your camera are e.g. green and just a quarter of them each red and blue (that's a common ratio for the colors). The camera then 'fakes' having a full set of RGB pixels by demosaicing, see https://en.wikipedia.org/wiki/Demosaicing https://en.wikipedia.org/wiki/Demosaicing ). Taking monochrome image with physical color filters would allow to use the full resolution of the camera for each color channel.
- qayxc 5y ago
  That's exactly what I wrote, though. > From what I know sensors do not have different readouts for the different color channels. You know wrong then. HST uses three camera sensors precisely to have three different filters at the same time and at full resolution: https://www.stsci.edu/hst/instrumentation/legacy/wfpc2 https://www.stsci.edu/hst/instrumentation/legacy/wfpc2 So yes, the WF/PC2 does indeed have different readouts per channels because each channel has its own dedicated sensor. Maybe you simply misinterpreted what I wrote. The fact of the matter is that consumer level sensors return multi-channel images (the sub-pixel filtering is an irrelevant technical detail), while scientific instruments use dedicated sensors per channel. edit: just to clarify even further - there are no subpixel shenanigans with scientific instruments for both higher precision and to avoid cross-talk between frequency bands; hence separate sensors per frequency filter. if you want multiple channels at once (e.g. space telescopes), you therefore need multiple sensors as opposed subpixel filtering.
  - _Microft 5y ago
    OK, I think I understand the confusion now. I understood "readout" as hardware implementation detail (think: "readout circuit") while it seems to refer to the data of a particular channel, right? My lack of familiarity with the lingo seems to blame then. That "subpixel shenanigans" on scientific apparatuses are inacceptable should be understood.