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Phones are already better at taking non-blurry pictures in very low light. They generally have pretty fast shutter speeds available for moving subjects. Dynamic

by foldr 6y ago

Phones are already better at taking non-blurry pictures in very low light. They generally have pretty fast shutter speeds available for moving subjects. Dynamic range is not particularly important now that exposure blending works so well. Diffraction all comes out in the wash. Smaller sensors allow wider apertures (and phones have some room to grow in terms of sensor size). The resolution advantage is actually quite moderate (people are often mislead by comparing the number of pixels rather than its square root).

sudosysgen 6y ago
If you use multiple exposures for exposure blending you lose sensitivity, and in the case of fast shutter speeds image quality plummets. Phones are simply not better at taking non-blury pictures in very lowlight. Cameras evolved since the 90s, we have 5 stops of IS, sharp f/1.4 lenses and exposure stacking. The resolution advantage is not moderate at all. A 12MP phone is around as sharp as a theoretically perfect 8MP sensor with a perfect lens, while current cameras are as sharp as 40+MP perfect sensor with a theoretically perfect lens. Diffraction absolutely doesn't come out as a wash. What matters is the actual diameter of the aperture, not the ratio. Phones are a tenth of ILCs in this metric, or even less for non-optimal focal lengths.
- foldr 6y ago
  >Diffraction absolutely doesn't come out as a wash. What matters is the actual diameter of the aperture, not the ratio It's actually the f stop that matters for diffraction, not the absolute diameter. Roughly, this is because the light spreads more with a longer focal length because it has a longer distance over which to diverge. If you crunch the numbers this exactly compensates for the larger absolute diameter of the aperture. Here is a post with a reference: https://www.dpreview.com/forums/thread/21428 https://www.dpreview.com/forums/thread/21428 It's amazing how much enthusiast discussion about cameras is based on basic misconceptions about optics.
  - sudosysgen 6y ago
    I'm not talking about linear resolution. I'm talking about angular resolution. Here, the airy disk diameter is the image size. At the same magnification, the image height is proportional to the object size. Since when the f number is smaller, at the same magnification, substituting in the thin lens formula with the magnification, you find that the object size is inversely proportional to the focal length. From this you come to the conclusion that, at the same focus distance, the smallest object you can image is a function of the absolute diameter of the aperture. Intuitively, this is because even though the airy disk has the same size, the focal length is much smaller, therefore the field of view is much wider for the same sensor size, therefore the angular confusion is much bigger, therefore for the same FoV at the same f number detail goes down. Or put another way, yes the light spreads more, but the sensor on a camera is bigger, so in the end you have much more detail anyways. This is why, for example, spy satellites despite operating at f/11 or so can resolve much more detail than a cellphone :) This is a standard exam question if you ever take a Wave Optics class, by the way. But as you say, enthusiast discussion, such as on DPReview, is often based on basic misconceptions about optics :)
    - foldr 6y ago
      Apologies for the snark. This would probably be a fun discussion in person. In my experience, most apparent disagreements like this just come down to confusion over which factors are being held constant out of field of view, sensor size, focal length, total amount of light gathered, etc. etc. If the phone was using a slice of a DSLR sensor, then yes, the absolute aperture would be what was relevant, as you obviously cannot improve the resolution of an image merely by cropping it (if you imagine a ultra ultra wide DSLR lens which becomes a normal phone lens after the crop). But two points: First, you're then comparing resolution at a focal length that's irrelevant to DSLRs, so in practical terms it's not a like for like comparison. Second, phones are using sensors with higher pixel density. The question is just whether the phone can use a wide enough fixed aperture to avoid being limited by diffraction at the desired resolution. A fixed aperture of e.g. f1.6 is practical at phone focal lengths but not (as a fixed aperture) at full frame focal lengths. If you calculate the theoretical linear resolution limit imposed by phone camera f-numbers, it's approaching 1000 lp/mm for the better models (e.g. an iPhone with an f1.6 aperture and a ~10mm sensor). I'm sure the real limits are lens aberrations and noise at the moment.

by foldr 6y ago

sudosysgen 6y ago

If you use multiple exposures for exposure blending you lose sensitivity, and in the case of fast shutter speeds image quality plummets. Phones are simply not better at taking non-blury pictures in very lowlight. Cameras evolved since the 90s, we have 5 stops of IS, sharp f/1.4 lenses and exposure stacking. The resolution advantage is not moderate at all. A 12MP phone is around as sharp as a theoretically perfect 8MP sensor with a perfect lens, while current cameras are as sharp as 40+MP perfect sensor with a theoretically perfect lens. Diffraction absolutely doesn't come out as a wash. What matters is the actual diameter of the aperture, not the ratio. Phones are a tenth of ILCs in this metric, or even less for non-optimal focal lengths.

foldr 6y ago
>Diffraction absolutely doesn't come out as a wash. What matters is the actual diameter of the aperture, not the ratio It's actually the f stop that matters for diffraction, not the absolute diameter. Roughly, this is because the light spreads more with a longer focal length because it has a longer distance over which to diverge. If you crunch the numbers this exactly compensates for the larger absolute diameter of the aperture. Here is a post with a reference: https://www.dpreview.com/forums/thread/21428 https://www.dpreview.com/forums/thread/21428 It's amazing how much enthusiast discussion about cameras is based on basic misconceptions about optics.
- sudosysgen 6y ago
  I'm not talking about linear resolution. I'm talking about angular resolution. Here, the airy disk diameter is the image size. At the same magnification, the image height is proportional to the object size. Since when the f number is smaller, at the same magnification, substituting in the thin lens formula with the magnification, you find that the object size is inversely proportional to the focal length. From this you come to the conclusion that, at the same focus distance, the smallest object you can image is a function of the absolute diameter of the aperture. Intuitively, this is because even though the airy disk has the same size, the focal length is much smaller, therefore the field of view is much wider for the same sensor size, therefore the angular confusion is much bigger, therefore for the same FoV at the same f number detail goes down. Or put another way, yes the light spreads more, but the sensor on a camera is bigger, so in the end you have much more detail anyways. This is why, for example, spy satellites despite operating at f/11 or so can resolve much more detail than a cellphone :) This is a standard exam question if you ever take a Wave Optics class, by the way. But as you say, enthusiast discussion, such as on DPReview, is often based on basic misconceptions about optics :)
  - foldr 6y ago
    Apologies for the snark. This would probably be a fun discussion in person. In my experience, most apparent disagreements like this just come down to confusion over which factors are being held constant out of field of view, sensor size, focal length, total amount of light gathered, etc. etc. If the phone was using a slice of a DSLR sensor, then yes, the absolute aperture would be what was relevant, as you obviously cannot improve the resolution of an image merely by cropping it (if you imagine a ultra ultra wide DSLR lens which becomes a normal phone lens after the crop). But two points: First, you're then comparing resolution at a focal length that's irrelevant to DSLRs, so in practical terms it's not a like for like comparison. Second, phones are using sensors with higher pixel density. The question is just whether the phone can use a wide enough fixed aperture to avoid being limited by diffraction at the desired resolution. A fixed aperture of e.g. f1.6 is practical at phone focal lengths but not (as a fixed aperture) at full frame focal lengths. If you calculate the theoretical linear resolution limit imposed by phone camera f-numbers, it's approaching 1000 lp/mm for the better models (e.g. an iPhone with an f1.6 aperture and a ~10mm sensor). I'm sure the real limits are lens aberrations and noise at the moment.