> Think about how little those 16MP digicams with pea-sized sensors are
> actually resolving at perhaps any aperture. Even the Minolta A1 with
> it's largish 5MP sensor (1/4 the size of 4/3) is diffraction limited at
> about f/4.5 Ugh!
According to the math, you are correct. The AA filter (of which the A1
has precious little of) helps defeat most sharpness at this level
anyway. In my experience with the A1, there was no discernable
difference at 100% viewing and with maximum AA-correcting sharpness
applied, between F4 and F7.1. All apertures between those apertures
were identical in my camera. F2.8 being a little haphazard and F8
being the point where diffraction blurring kicked in and became
visible.
The point, which I want to make here, is that once you apply the
appropriate sharpening at the pixel level to correct for the AA filter
and Bayer matrixing, we also end up correcting for a some of the
diffraction blurring too.
Another factor which the math calculations don't accomodate. The
diffraction calculations, as well as the DoF calculations assume
grid-positioned subject detail. The reality is that even a point
source light will fall across two or more pixels because it will
usually fall at the transition point between sensels.
The theoretical and the actual don't always match.
AG
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|