I’m curious about the opposite of the usual “fastest lens” question: among production imaging lenses, what is the highest finite f-number actually offered? Specifically: - What’s the highest minimum aperture (smallest opening) commonly found on a production lens? - What’s the highest absolute f-number reached by a production lens, including unusual but real production optics? I’m interested in actual manufactured lenses or imaging optics, not theoretical limits.

What is the smallest aperture (highest f-number) found on production lenses?

Asked 1/24/2017

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I’m curious about the opposite of the usual “fastest lens” question: among production imaging lenses, what is the highest finite f-number actually offered?

Specifically:

What’s the highest minimum aperture (smallest opening) commonly found on a production lens?
What’s the highest absolute f-number reached by a production lens, including unusual but real production optics?

I’m interested in actual manufactured lenses or imaging optics, not theoretical limits.

lenses diffraction aperture f-number medium-format

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

9y ago

2 Answers

I'm stretching the definition of "lens" a bit, but certainly the slowest imaging device you can buy is a 1-micron precision pinhole. See for example the products from Thorlabs.
Any smaller than that (and practically speaking, any smaller than about 5 microns) and diffraction effects will ruin your image. :-) .

Originally by user25396. Source · Licensed CC BY-SA 4.0

user25396

9y ago

AI Answer

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For conventional photographic lenses, very small apertures like f/45 do exist. Examples mentioned include several Hasselblad lenses that stop down to f/45.

If you broaden “lens” to include specialized imaging optics, much higher f-numbers are possible. One answer cites the Cooke PS945 reaching f/90, which is far beyond typical still-photo lenses.

If you stretch the definition further to pinhole imaging devices, the effective f-number can be much higher still. Extremely small precision pinholes are available, but at that point diffraction dominates and image quality drops sharply.

So, based on the answers provided:

A high but plausible figure for conventional production photo lenses is around f/45.
For specialized production imaging optics, f/90 is a cited example.
Pinhole devices can exceed that in effective f-number, but they’re a special case rather than a normal lens.

In practice, very high f-numbers are uncommon because diffraction softening becomes severe long before they become broadly useful.

What is the smallest aperture (highest f-number) found on production lenses?

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