Aperture question, re: sharpness

Started Feb 26, 2014 | Questions thread
William Porter Senior Member • Posts: 1,676
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2

You've gotten the answers. To summarize.

  1. No, a lens is NOT going to be at its sharpest stopped all the way down to, say, f/22. At some point most lenses become subject to diffraction. I shoot past f/11 only when I I'm already at 1/4000th sec and ISO 200 or 100 and have no other choice. Ansel Adams and the other members of Group f/64  took that name because they had to go to f/64 to get decent depth of field on their huge cameras; but things have changed a lot.
  2. Most lenses have a "sweet spot" — an aperture (and if its a zoom lens, a focal length) that provides the best optical performance. Where this sweet spot is varies from lens to lens. DxO or the manufacturer's own statistics might help you find it for your lenses. The common rule of thumb is that for most lenses, the sweet spot on a prime lens is not wide open, but stopped down one or two stops. So if you've got an f2.8 lens, the sweet spot might be f4.5 or f5.6. But it varies.
  3. A good lens's sweet spot won't be dramatically better than the other apertures, that is, buy good lenses and you can more or less stop worrying about this problem.

Now if you want sharp pictures, the best thing you can do doesn't necessarily cost any money at all: Understand how to light your photos well. It's kind of absurd to say that "good light trumps good glass" — you'd always prefer to have both — but it feels true nonetheless. There are other things that can help your photos get sharper: tripod, appropriately faster shutter speeds and others. But better lighting is just about the best way to improve the sharpness of your photos, especially if better lighting allows you to reduce your camera's ISO to its optimal setting and/or increase your shutter speed.

Final point: Sharpness is just about the least interesting aspect of a good photo.

Will

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