4 ms·

At what point do you start seeing diminishing return on pixel-count with such a small sensor? (Or can you always get value if you're willing to bump up your exp

At what point do you start seeing diminishing return on pixel-count with such a small sensor? (Or can you always get value if you're willing to bump up your exposure time)

zimpenfish 5y ago
I guess if you don't mind reducing the resolution, you can e.g. average 4 pixels to reduce the noise (but I don't know if that gives you a lower noise floor than just a 16MP sensor in the first place...)
- tomtom1337 5y ago
  You would actually have more noise, or at least, not less noise. There is readout noise associated with reading the information out from each pixel. Using one bigger pixel would give you less noise than four smaller ones :)
  - zimpenfish 5y ago
    I'm no physics or optics expert but this paper seems to suggest you're wrong? https://www.sciencedirect.com/science/article/pii/S0263224119311893 https://www.sciencedirect.com/science/article/pii/S026322411... "...show that an array of small independent sensors is always less noisy than a large sensor of the same size."
    - tomtom1337 5y ago
      So it would seem! Thanks!
  - namibj 5y ago
    The summed value scales linearly with the pixel count but the combined readout noise only with the square root of the pixel count. Though, there are indeed other reasons to prefer a 16MP sensor in the first place (most notably, dynamic range, but also allowing slower readout).
uuyi 5y ago
It’s mostly a problem of pixel size. The smaller the pixels the less light the pixels get. That means really terrible low light performance. And no software can’t magically make that as good as a pixel 4x the size. The only advantage here is it allows you to get away with more crime like cropping and digital zoom in brighter lights. That may be an advantage depending on the application. I’d rather have a 12MP sensor twice that size with some glass in front though for most applications. Far more useful.
- tonyarkles 5y ago
  > with some glass in front though Since it sounds like you're familiar with the field, any chance you've come across a CS- or C-mount lens with an autofocus motor? I've looked around a bunch and haven't had much luck. The current solution is a full C-mount-to-Canon-EF-mount adapter that has drive electronics in it, but it's eye-wateringly expensive and huge & heavy.
  - uuyi 5y ago
    Haven’t gone near those mounts. All mine is Z mount recently and F mount going back to the dark ages.
  - neetdeth 5y ago
    Never had a reason to use them, but I do recall that Edmund Optics has some C-mount units with liquid lenses in their catalog. The driver modules will allow control over USB or I2C.
    - LeifCarrotson 5y ago
      I've used them in some industrial vision applications with Dalsa cameras. They worked fine, I would have preferred a fixed focus and a manual adjustment when the requirements changed (it was much more difficult to get good real-unit measurements and to compensate for distortion) but they worked fine.
      - 5y ago
gswdh 5y ago
colechristensen 5y ago
This camera does indeed have too many pixels. If you use the Rayleigh criterion to calculate the maximum angular resolution based on aperture (θ = 1.22 * λ / d) using green light for the wavelength (and focal length / focal ratio to get the aperture) and use the resulting angular resolution and the given diagonal 84 degree field of view... you end up getting that there are about half as many pixels as the maximum theoretical angular resolution. Combined with lens imperfections and other sources of distortion (as opposed to the other commenters talking about exposure times) the result is that the extra pixels are really probably not adding any new information, or that they're right at the levels of diminishing returns where the returns are more or less zero for extra pixels. >can you always get value if you're willing to bump up your exposure time No, there are hard limits on how much extra information you can get with more exposure time.
- rich_sasha 5y ago
  What about pixel size compared to light wavelength? If my maths is right, 7.4mm sensor side divided by 9,150 pixels is about 800nm size. Visible light is 400-700nm. And presumably not all of the pixel is actually light-sensitive. Is this a valid comparison though? I’m not good at quantum...
  - tomtom1337 5y ago
    The Rayleigh criterion above is exactly what is used to answer the question you're asking :) it tells you what size objects you can resolve with a given wavelength of light, which if you think about it in a different manner also tells you what the smallest useful pixel size you can have is. Two smaller pixels next to one another would be able to distinguish no more information than a combined one.
    - namibj 5y ago
      Actually, that's not true. However, going beyond requires deconvolution of the wavelength-scaling diffraction pattern, so it's only practical if you have narrowband radiation (stops working at 10~20% FWHM bandwidth). Suitable sources include monochromatic LEDs, most lasers, and some gas discharge lamps (notably low pressure sodium).

At what point do you start seeing diminishing return on pixel-count with such a small sensor? (Or can you always get value if you're willing to bump up your exposure time)

zimpenfish 5y ago

I guess if you don't mind reducing the resolution, you can e.g. average 4 pixels to reduce the noise (but I don't know if that gives you a lower noise floor than just a 16MP sensor in the first place...)

tomtom1337 5y ago
You would actually have more noise, or at least, not less noise. There is readout noise associated with reading the information out from each pixel. Using one bigger pixel would give you less noise than four smaller ones :)
- zimpenfish 5y ago
  I'm no physics or optics expert but this paper seems to suggest you're wrong? https://www.sciencedirect.com/science/article/pii/S0263224119311893 https://www.sciencedirect.com/science/article/pii/S026322411... "...show that an array of small independent sensors is always less noisy than a large sensor of the same size."
  - tomtom1337 5y ago
    So it would seem! Thanks!
- namibj 5y ago
  The summed value scales linearly with the pixel count but the combined readout noise only with the square root of the pixel count. Though, there are indeed other reasons to prefer a 16MP sensor in the first place (most notably, dynamic range, but also allowing slower readout).

uuyi 5y ago

It’s mostly a problem of pixel size. The smaller the pixels the less light the pixels get. That means really terrible low light performance. And no software can’t magically make that as good as a pixel 4x the size. The only advantage here is it allows you to get away with more crime like cropping and digital zoom in brighter lights. That may be an advantage depending on the application. I’d rather have a 12MP sensor twice that size with some glass in front though for most applications. Far more useful.

tonyarkles 5y ago
> with some glass in front though Since it sounds like you're familiar with the field, any chance you've come across a CS- or C-mount lens with an autofocus motor? I've looked around a bunch and haven't had much luck. The current solution is a full C-mount-to-Canon-EF-mount adapter that has drive electronics in it, but it's eye-wateringly expensive and huge & heavy.
- uuyi 5y ago
  Haven’t gone near those mounts. All mine is Z mount recently and F mount going back to the dark ages.
- neetdeth 5y ago
  Never had a reason to use them, but I do recall that Edmund Optics has some C-mount units with liquid lenses in their catalog. The driver modules will allow control over USB or I2C.
  - LeifCarrotson 5y ago
    I've used them in some industrial vision applications with Dalsa cameras. They worked fine, I would have preferred a fixed focus and a manual adjustment when the requirements changed (it was much more difficult to get good real-unit measurements and to compensate for distortion) but they worked fine.
    - 5y ago

gswdh 5y ago

colechristensen 5y ago

This camera does indeed have too many pixels. If you use the Rayleigh criterion to calculate the maximum angular resolution based on aperture (θ = 1.22 * λ / d) using green light for the wavelength (and focal length / focal ratio to get the aperture) and use the resulting angular resolution and the given diagonal 84 degree field of view... you end up getting that there are about half as many pixels as the maximum theoretical angular resolution. Combined with lens imperfections and other sources of distortion (as opposed to the other commenters talking about exposure times) the result is that the extra pixels are really probably not adding any new information, or that they're right at the levels of diminishing returns where the returns are more or less zero for extra pixels. >can you always get value if you're willing to bump up your exposure time No, there are hard limits on how much extra information you can get with more exposure time.

rich_sasha 5y ago
What about pixel size compared to light wavelength? If my maths is right, 7.4mm sensor side divided by 9,150 pixels is about 800nm size. Visible light is 400-700nm. And presumably not all of the pixel is actually light-sensitive. Is this a valid comparison though? I’m not good at quantum...
- tomtom1337 5y ago
  The Rayleigh criterion above is exactly what is used to answer the question you're asking :) it tells you what size objects you can resolve with a given wavelength of light, which if you think about it in a different manner also tells you what the smallest useful pixel size you can have is. Two smaller pixels next to one another would be able to distinguish no more information than a combined one.
  - namibj 5y ago
    Actually, that's not true. However, going beyond requires deconvolution of the wavelength-scaling diffraction pattern, so it's only practical if you have narrowband radiation (stops working at 10~20% FWHM bandwidth). Suitable sources include monochromatic LEDs, most lasers, and some gas discharge lamps (notably low pressure sodium).