5 ms·

I noticed that the new iphone 12 has a f/2.0 aperture telephoto lens whereas my existing iphone XS has a f/2.4 aperture telephoto lens. What are the implicatio

by ahnick 6y ago

I noticed that the new iphone 12 has a f/2.0 aperture telephoto lens whereas my existing iphone XS has a f/2.4 aperture telephoto lens. What are the implications of this? I always understood that for a telephoto lens you wanted the f-stop number to be higher, so that the image is clearer since the subject is at a greater distance. My gut instinct is that the iphone XS/XR lens might capture a sharper initial image, but maybe the final product won't be as good as the newer lens do to all the processing being done by the phone? Perhaps a bigger diameter on the telephoto lens is better for night mode shooting, so more light is being captured? Hoping someone more knowledgeable than I can weigh in. :)

hgo 6y ago
A lower f-stop number means that the aperture is bigger (relative to the focal length), such that it let's in more light. This has several subjective benefits: more light can be used for shorter exposure time or lower ISO (sensor gain) each leading to a sharper image. Also, it creates a shallower depth of field or "more blur" which separates the subject for a more pleasing picture. (This may be irrelevant on sensors as small as on a phone, which counteract shallow depth of field effects.) It may reduce the image quality if the lens of of lower quality, as it is more expensive to build large-aperture lenses.
terramex 6y ago
Lower f-number means that lens captures more light and has less depth-of-field (more blurred background and foreground). For small sensors like in iPhone DoF is huge anyway and planes separation has to be faked in post-processing. In general less f-number is better.
mullingitover 6y ago
> I always understood that for a telephoto lens you wanted the f-stop number to be higher, so that the image is clearer since the subject is at a greater distance. You want the lowest f-stop number possible for telephoto, so you have more available light hitting the sensor. This allows you to get a higher shutter speed. The higher shutter speeds compensate for the exaggerated shake you get from the longer lens.
- ahnick 6y ago
  If this is the case, then can we infer that the iphone 12 pro has a slightly better telephoto lens than the iphone 12 pro max? (The max's f-stop is listed as f/2.2)
  - mullingitover 6y ago
    The lens is better, yes, however the sensor on the pro max is significantly larger, so I think it's basically a wash.
centimeter 6y ago
> I always understood that for a telephoto lens you wanted the f-stop number to be higher, I suspect you are confusing f-stop (ratio of aperture diameter to focal length) and focal length ("zoom"). Also the f-stop marketing is annoying to me - the f/2.4 aperture on an iPhone lens is probably equivalent to like f/22 on an FF lens for most purposes.
andrewstuart2 6y ago
The aperture doesn't necessarily have a theoretical effect on image quality, though it will certainly impact the depth of field, and will be shallower at higher focal lengths for the same f-stop. Also, in practice, due to impurities and imperfections in glass and other inefficiencies, there will be effects, though they can definitely be managed and are always trade-offs. Usually with aperture it's well worth it to increase the aperture. What you'll find with professional glass lenses, with variable apertures, is that sometimes you do need to decrease the aperture (higher f-stop) to get the sharpest possible image from the lens. At wider apertures you're collecting more light, from closer to the edges of the glass, at higher refractory angles, travelling through more glass, and thus sharpness goes down. The other side of the aperture though, aside from DOF, is that it lets more light through, so you will also get more flexibility in general on trading off proper exposure time vs motion blur, which is great for low light handheld photography. I would expect for mobile lenses, though, since they know it's a fixed aperture, they've done their best to mitigate those effects, aside from the fact that your DOF is definitely fixed since there's no variable aperture on your phone camera lens. Honestly the only way to know for sure is wait for somebody like DPReview to run the camera through their test suite and get some objective numbers/photos to see what, if any, impact there is from the wider aperture. A DOF calculator can be a helpful resource to get a gut feel for the relationship between the various inputs that affect DOF. e.g. https://www.photopills.com/calculators/dof https://www.photopills.com/calculators/dof
acomjean 6y ago
as others have said, the lower the f stop the more light the lens lets in. lower is almost always better, (But makes lenses bigger and heavier). The amount of light halves as the f stop goes up, but its in steps. 1.4/2/2.8/4/5.6 . so the difference is about 1/2 stop, not huge. As you close the lens iris (the f stop # goes up) you get more of the image "in focus", so focus doesn't need to be as precise. But you'll need a minimum shutter speed so moving objects in the frame don't blur. wikipedia has a good photo example of this. https://en.wikipedia.org/wiki/Depth_of_field#Effect_of_lens_aperture https://en.wikipedia.org/wiki/Depth_of_field#Effect_of_lens_...

by ahnick 6y ago

hgo 6y ago

A lower f-stop number means that the aperture is bigger (relative to the focal length), such that it let's in more light. This has several subjective benefits: more light can be used for shorter exposure time or lower ISO (sensor gain) each leading to a sharper image. Also, it creates a shallower depth of field or "more blur" which separates the subject for a more pleasing picture. (This may be irrelevant on sensors as small as on a phone, which counteract shallow depth of field effects.) It may reduce the image quality if the lens of of lower quality, as it is more expensive to build large-aperture lenses.

terramex 6y ago

Lower f-number means that lens captures more light and has less depth-of-field (more blurred background and foreground). For small sensors like in iPhone DoF is huge anyway and planes separation has to be faked in post-processing. In general less f-number is better.

mullingitover 6y ago

> I always understood that for a telephoto lens you wanted the f-stop number to be higher, so that the image is clearer since the subject is at a greater distance. You want the lowest f-stop number possible for telephoto, so you have more available light hitting the sensor. This allows you to get a higher shutter speed. The higher shutter speeds compensate for the exaggerated shake you get from the longer lens.

ahnick 6y ago
If this is the case, then can we infer that the iphone 12 pro has a slightly better telephoto lens than the iphone 12 pro max? (The max's f-stop is listed as f/2.2)
- mullingitover 6y ago
  The lens is better, yes, however the sensor on the pro max is significantly larger, so I think it's basically a wash.

centimeter 6y ago

> I always understood that for a telephoto lens you wanted the f-stop number to be higher, I suspect you are confusing f-stop (ratio of aperture diameter to focal length) and focal length ("zoom"). Also the f-stop marketing is annoying to me - the f/2.4 aperture on an iPhone lens is probably equivalent to like f/22 on an FF lens for most purposes.

andrewstuart2 6y ago

The aperture doesn't necessarily have a theoretical effect on image quality, though it will certainly impact the depth of field, and will be shallower at higher focal lengths for the same f-stop. Also, in practice, due to impurities and imperfections in glass and other inefficiencies, there will be effects, though they can definitely be managed and are always trade-offs. Usually with aperture it's well worth it to increase the aperture. What you'll find with professional glass lenses, with variable apertures, is that sometimes you do need to decrease the aperture (higher f-stop) to get the sharpest possible image from the lens. At wider apertures you're collecting more light, from closer to the edges of the glass, at higher refractory angles, travelling through more glass, and thus sharpness goes down. The other side of the aperture though, aside from DOF, is that it lets more light through, so you will also get more flexibility in general on trading off proper exposure time vs motion blur, which is great for low light handheld photography. I would expect for mobile lenses, though, since they know it's a fixed aperture, they've done their best to mitigate those effects, aside from the fact that your DOF is definitely fixed since there's no variable aperture on your phone camera lens. Honestly the only way to know for sure is wait for somebody like DPReview to run the camera through their test suite and get some objective numbers/photos to see what, if any, impact there is from the wider aperture. A DOF calculator can be a helpful resource to get a gut feel for the relationship between the various inputs that affect DOF. e.g. https://www.photopills.com/calculators/dof https://www.photopills.com/calculators/dof

acomjean 6y ago

as others have said, the lower the f stop the more light the lens lets in. lower is almost always better, (But makes lenses bigger and heavier). The amount of light halves as the f stop goes up, but its in steps. 1.4/2/2.8/4/5.6 . so the difference is about 1/2 stop, not huge. As you close the lens iris (the f stop # goes up) you get more of the image "in focus", so focus doesn't need to be as precise. But you'll need a minimum shutter speed so moving objects in the frame don't blur. wikipedia has a good photo example of this. https://en.wikipedia.org/wiki/Depth_of_field#Effect_of_lens_aperture https://en.wikipedia.org/wiki/Depth_of_field#Effect_of_lens_...