Don't forget that at about f8 diffraction effects will begin to rear
it's ugly head. So if your maximum aperture is 4.0 diffraction will
start to steal sharpness using that two stops down rule of thumb. It's
worse the shorter the lens gets as the actual physical aperture is what
controls diffraction, (and DOF as well).
On 6/4/2012 6:22 PM, Larry Colen wrote:
I was thinking about my quest for sharpness, and was considering trying to do some
research into what the aperture "sweet spot" is for each lens, and was
wondering if anyone had already made a chart of them.
Then I wondered how much it really matters. I've heard "a couple of stops down from wide
open", "anywhere between f/8 and f/16", and a couple other rules of thumb. I do
know that on some lenses, particularly the FA50/1.4, that stopping it down a couple of stops from
wide open, makes a huge difference. And I suspect that if you look on an MTF chart, you might be
able to easily see the difference between f/4 and f/8, but is there a practical noticeable
difference?
There is also the question of sharpness at the critical focus distance, and
overall sharpness. That a lens might be sharper at f/4 than f/16 at the focal
distance, but with a lot more depth of field, more of the photo will be sharper
at f/16, than at f/64.
I'm primarily interested in answers based on personal, practical experience,
rather than theory. My hunch is that as long as I'm not too close to wide
open, or pushing diffraction limits, optimizing aperture for sharpness is not
the most productive place to spend my time and energy. That I'm generally best
optimizing the aperture for the picture, and not trying to optimize the
aperture for MTF.
--
Larry Colen [email protected] sent from i4est
--
Don't lose heart! They might want to cut it out, and they'll want to avoid a
lengthily search.
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