Best aperture setting?

Question

Is it still true (now with digital) that one gets their best aperture
setting about 3 F stops from it's widest opening. My widest opening is F2.8. In 35mm photography 3 stops down from F2.8 would be F5.6 So even on my camera which has settngs of F2.8, 3.2, 4.0, 4.5, 5.0, 5.6, 6.3, 7.1 and F8; my best setting for image quality would still be F/5.6? Again does this still hold true for digital photography?

Answer 1

Your rule-of-thumb that best sharpness is found 3 stops smaller than the widest aperture of a lens is still a good rule-of-thumb. Lens physics and optics haven't changed from when the world was full of film cameras.

Note that it's just a rule-of-thumb. It's not science. The best way to know what aperture your lens gets optimal sharpness is to shoot it at every aperture and look for yourself! That's certainly a difference between digital and film - you can experiment with your lens and see the results right away!


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Disclosure: I am the owner of www.lenslenders.com in Canada.

Answer 2

But here's a thought...

The old idea of stopping down for a better image deals with problems near the edge of the frame, as the center of the frame is nearly always good at any aperture.

If you are using a "classic" lens (non-DX, non-Di, etc.) designed for a full format camera, such as 35 mm film, you will not have those outer edges on the image sensor anyhow and (I predict) that you would not see any benefit from stopping down a bit. You are only capturing the "sweet spot" in the denter of the lens anyhow. Do some tests of your own (digital is free) and report back to us. :-)

Answer 3

If you look at a cross-section of all 35mm and medium format lens tests online, I think you will quickly come to the conclusion that best performance occurs at f8, no matter what the maximum aperture.

However, these lenses go to f16 or even f32. If your aperture choice ends at f8 I would think that f5.6 might indeed be the sweet spot.

Answer 4

As a rule of thumb, that sounds about right. Two or three stops. Film vs. digital doesn't matter - this is a function of the lens itself. Except... 3 stops down from f/2.8 is f/8. The full stops are:
1.0
1.4
2.0
2.8
4.0
5.6
8.0
etc... Just remember 1.0 and 1.4. From there you can double the values for the next two f-stops and repeat.
(If you knew this, and typing f/5.6 was a brainfart, I beg your pardon :-)