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For those who may not be aware: digital cameras capture a grayscale image with a single value per pixel. The image sensor is covered by an array of colour filte

For those who may not be aware: digital cameras capture a grayscale image with a single value per pixel. The image sensor is covered by an array of colour filters (red, green, blue) in a pattern called the Bayer pattern. Typically, one row of filters will alternate RGRGRGRGRG and the next row will alternate GBGBGBGBGB. "Debayering" involves interpolating the colour-filtered grayscale values of neighbouring pixels into each pixel, and then often applying some software filtering to remove dead pixels, noise, and sharpen the image.

bruce343434 4y ago
Doesn't that mean green is over represented per area? Why not something like RGBRGBRGB GBRGBRGBR BRGBRGBRG
- mafuy 4y ago
  The human eye is particularly sensitive to green. This is also why the 5:6:5 encoding of RGB has its focus on green.
  - fomine3 4y ago
    Also why Pentile OLEDs exist
- verall 4y ago
  Green is in the middle of the spectrum so it is the best for detecting amount of light. Color is determined by the G-R and G-B ratios. There are sensors with more esoteric Bayer filters, like to better capture in low light there are sensors which replace one of the G's with an N (neutral light / "no" color filter)
jeffbee 4y ago
Aren't there still plenty of cameras using 3 separate sensors and an optical beam splitter, instead of a Bayer filter array?
- jakebasile 4y ago
  I don't know of any consumer cameras that do this. Some manufacturers use a different filter on some models, Fuji uses an X-Trans filter on some models which in the past can cause issues with some software demosaicing.
  - rplst8 4y ago
    X-trans is still a mosaic and the underlying tech is mostly the same (color filter array with monochrome "buckets"). Instead of a 2x2 pattern, it uses a 6x6 pattern. Goes something like: GRBGBR BGGRGG RGGBGG Instead of: RG GB
- kelsolaar 4y ago
  Consumers camera use a Bayer colour filter array because it is cheaper and more compact. Demosaicing is performant enough for most consumer applications that it is hard to justify for anything than scientific applications. As a matter of fact, even Motion Picture cameras, e.g. ARRI LF, are using a Bayer CFA.
- formerly_proven 4y ago
  If they do, that has to be limited to "broadcast" cameras. Digital cinema cameras all pretty prominently use a single sensor.
- kuschku 4y ago
  There is one model still sold by sony using these! https://pro.sony/en_GB/products/shoulder-camcorders/pxw-z750 https://pro.sony/en_GB/products/shoulder-camcorders/pxw-z750 All the others have now switched to bayer sensors.
  - aidenn0 4y ago
    Only $3k from Adorama; are pro cameras really that cheap these days? [edit] That was google shopping popping up the Z150, which is presumably less expensive. The Z450 is 20k, body only, and the Z750 is "in store purchase only"
irthomasthomas 4y ago
This means that the true resolution of digital cameras is roughly one third of the advertised megapixel value, depending on the exact Bayer matrix design.
- andy_ppp 4y ago
  Well that’s sort of true but the algorithms that decide on which pixel has which colour are better than just the number of underlying RGB pixels…
- _ph_ 4y ago
  It is roughly half of the pixel count, as the Bayer interpolation gives better resolution than a naive conversion. Also, a lot of detail is in the green channel, which is registered by half of the total pixels.
- SiempreViernes 4y ago
  Only if you consider raw pixel count in a single channel as the only "true" measure.
- verall 4y ago
  The true resolution of digital cameras isn't measured in pixels, it's measured in cycles per pixel and then related to the sensor size and pixel pitch[0]. Camera sensor pixels are not squares like the pixels in a digital image, they are point samples. You can then interpolate from the point samples onto an arbitrary number of digital pixels, so what matters is basically how close you can still see edges between lines, which depends on more things than the sensor size. When megapixels are quoted for a digital camera, they are either quoting sensor size (resolution) (like on real engineering documentation) or they are just quoting the highest resolution digital image they think they can get away with the software producing (marketing, advertisements), which is arbitrary, which is part of why you do hear not to just select a camera with the most megapixels. It's a pretty deep topic and people do get degrees in basically just digital imaging. Not me though! I don't really understand most of this stuff... [0] https://www.image-engineering.de/library/technotes/742-units-and-conversions-for-resolution https://www.image-engineering.de/library/technotes/742-units...

bruce343434 4y ago

Doesn't that mean green is over represented per area? Why not something like RGBRGBRGB GBRGBRGBR BRGBRGBRG

mafuy 4y ago
The human eye is particularly sensitive to green. This is also why the 5:6:5 encoding of RGB has its focus on green.
- fomine3 4y ago
  Also why Pentile OLEDs exist
verall 4y ago
Green is in the middle of the spectrum so it is the best for detecting amount of light. Color is determined by the G-R and G-B ratios. There are sensors with more esoteric Bayer filters, like to better capture in low light there are sensors which replace one of the G's with an N (neutral light / "no" color filter)

jeffbee 4y ago

Aren't there still plenty of cameras using 3 separate sensors and an optical beam splitter, instead of a Bayer filter array?

jakebasile 4y ago
I don't know of any consumer cameras that do this. Some manufacturers use a different filter on some models, Fuji uses an X-Trans filter on some models which in the past can cause issues with some software demosaicing.
- rplst8 4y ago
  X-trans is still a mosaic and the underlying tech is mostly the same (color filter array with monochrome "buckets"). Instead of a 2x2 pattern, it uses a 6x6 pattern. Goes something like: GRBGBR BGGRGG RGGBGG Instead of: RG GB
kelsolaar 4y ago
Consumers camera use a Bayer colour filter array because it is cheaper and more compact. Demosaicing is performant enough for most consumer applications that it is hard to justify for anything than scientific applications. As a matter of fact, even Motion Picture cameras, e.g. ARRI LF, are using a Bayer CFA.
formerly_proven 4y ago
If they do, that has to be limited to "broadcast" cameras. Digital cinema cameras all pretty prominently use a single sensor.
kuschku 4y ago
There is one model still sold by sony using these! https://pro.sony/en_GB/products/shoulder-camcorders/pxw-z750 https://pro.sony/en_GB/products/shoulder-camcorders/pxw-z750 All the others have now switched to bayer sensors.
- aidenn0 4y ago
  Only $3k from Adorama; are pro cameras really that cheap these days? [edit] That was google shopping popping up the Z150, which is presumably less expensive. The Z450 is 20k, body only, and the Z750 is "in store purchase only"

irthomasthomas 4y ago

This means that the true resolution of digital cameras is roughly one third of the advertised megapixel value, depending on the exact Bayer matrix design.

andy_ppp 4y ago
Well that’s sort of true but the algorithms that decide on which pixel has which colour are better than just the number of underlying RGB pixels…
_ph_ 4y ago
It is roughly half of the pixel count, as the Bayer interpolation gives better resolution than a naive conversion. Also, a lot of detail is in the green channel, which is registered by half of the total pixels.
SiempreViernes 4y ago
Only if you consider raw pixel count in a single channel as the only "true" measure.
verall 4y ago
The true resolution of digital cameras isn't measured in pixels, it's measured in cycles per pixel and then related to the sensor size and pixel pitch[0]. Camera sensor pixels are not squares like the pixels in a digital image, they are point samples. You can then interpolate from the point samples onto an arbitrary number of digital pixels, so what matters is basically how close you can still see edges between lines, which depends on more things than the sensor size. When megapixels are quoted for a digital camera, they are either quoting sensor size (resolution) (like on real engineering documentation) or they are just quoting the highest resolution digital image they think they can get away with the software producing (marketing, advertisements), which is arbitrary, which is part of why you do hear not to just select a camera with the most megapixels. It's a pretty deep topic and people do get degrees in basically just digital imaging. Not me though! I don't really understand most of this stuff... [0] https://www.image-engineering.de/library/technotes/742-units-and-conversions-for-resolution https://www.image-engineering.de/library/technotes/742-units...