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Why do most lenses have a smallest aperture of F22?


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I know that the smaller the aperture, the greater the depth of field. However, it seems that most lenses have a sweet spot at around f11 and if you focus 1/3rd into the scene, this seems to give great images.

My Voightlander 50mm is interesting as it's aperture range is f2 to f16 with less significantly drop off after f11 than my Sony 28-105 G zoom at 50mm (not a fear comparison between a prime and a zoom)

Edited by thebeardedgroundsman
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I have lenses that only drop to f11, and others that go to f128.  Many manufacturers stop the scale at the point where diffraction is so bad, they don't want customers using that aperture setting.  On most lenses, the best resolution is in the f8 to f16 range -- but if you want more or less DOF for the subject, other f-stops will work fine.

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  • 1 month later...
On 10/31/2022 at 10:03 AM, thebeardedgroundsman said:

I know that the smaller the aperture, the greater the depth of field. However, it seems that most lenses have a sweet spot at around f11 and if you focus 1/3rd into the scene, this seems to give great images.

My Voightlander 50mm is interesting as it's aperture range is f2 to f16 with less significantly drop off after f11 than my Sony 28-105 G zoom at 50mm (not a fear comparison between a prime and a zoom)

You get a greater depth of field, that's true, but you also run into the diffraction limit, i.e. the sharpness decreases the further you close the aperture. This depends on the sensor resolution and aperture size. A good in depth explanation you can find here: https://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
It's also quite instructive to do a test series with some fine structured target (like e.g. a cushion from fine woven fabric) at different apertures. You start with the aperture opened to the max (e.g. ƒ/2.8) and close it further after each exposure. You will see that first the sharpness increases but there is a certain point when it decreases due to the diffraction limit. 
This is why you have sweet spots of sharpness with every lens, just not the same one for all lenses.

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