Do any lenses stop down smaller than f/32, and when is that useful?
Asked 5/30/2013
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Most lenses I use only stop down to around f/32. Do any lenses go smaller than that, such as f/45 or beyond? If so, what are those very small apertures useful for, and why aren’t they more common on 35mm/full-frame and smaller cameras?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
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Yes. For example, my sigma 105mm can go up to f/45. Basically, such small aperture can produce a very large DOF, but In most cameras and lenses combination the quality of the image starts to decrease after f/16 because of the diffraction of light, and usually the DOF at f/16 is large enough. I don't know what so special about the f/32 but i guess that in most cases the image quality with smaller aperture will decrease significantly and manufacturers don't see any advantage enabling smaller aperture.
If you're using such small aperture just to get a longer exposure, you should consider using an ND filter which reduce the amount of light. For example a 0.9ND (X3) will reduce 3 stops and that means X8 longer exposure with the same parameters, or same exposure with a bigger aperture.
You can get some pretty good ND filters that only transfer 1/1000 of the given light, thus, creating very long exposures even in the middle of the day.
For further information about diffraction and diffraction limit you may start here
Originally by user19909. Source · Licensed CC BY-SA 4.0
user19909
13y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. Some lenses do stop down smaller than f/32 — for example, certain macro and medium/large-format lenses may reach f/45 or narrower.
The key point is that f-numbers are ratios, not absolute hole sizes. On larger formats, a very small f-number like f/45 can still correspond to a physically larger opening than it would on a smaller format camera, so it can be useful for increasing depth of field.
On 35mm/full-frame and smaller sensors, very small apertures are less common because diffraction softening becomes significant. In many setups, image quality starts to decline noticeably after about f/16, and by f/32 or smaller the extra depth of field often isn’t worth the loss of sharpness.
That’s also why compact cameras often have maximum apertures only around f/8: their small sensors hit diffraction limits sooner.
If your goal is not more depth of field but simply a longer shutter speed, an ND filter is usually a better solution than stopping down to f/32 or smaller.
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