At 22:21 10/7/02, Winsor Crosby wrote:
It is rather strange, I have never seen a lens tested over 100lpmm in
Pop photo (some recent 10 year's lens test ) and Modern Photography
at:
http://brashear.phys.appstate.edu/lhawkins/photo/mp-zuiko-tests.txt
I have made a test on some Zuikos ten years ago, with the following
lenses tested only the 50/3.5 at F5.6 can resolve to 70lpmm:
16/3.6
24/2
35/2
50/1.4 S/N 3xx,xxx
50/3.5
85/2
135/2.8
Test target: CCITT chart for fax and photocopier.
Illumination: T32 at 45% to target.
OM4Ti on tripod, cable release.
Film: Fuji Velvia
Projection: Leica 255 with Colorplan P2 90/2.5 (project to 100 inch)
Microscope: M6x+WF10 eyepieces.
Apertures tested only wide open and F5.6
C.H.Ling
I was kind of surprised at those resolution figures too. Usually 70 to 80
lines per mm is considered very fine performance for a lens in published
tests. I have never seen results with 100 lines per mm.
That raises an interesting point though. Since the resolution of film
seems to be much higher than existing lens designs perhaps to focus on CCD
resolution equaling film resolution is incorrect. The limiting factor is
the lens, not the film. Perhaps all that is needed is a CCD that can
capture the resolution of the lens as film already does and the results
will be indistinguishable between the two systems.
--
Winsor Crosby
Long Beach, California
See the following:
http://people.smu.edu/rmonagha/mf/limits.html
YMMV using some of the techniques there. Film can easily exceed optical
limits. Rightly so. There is something to be said for other effects
gained in having it this way. Very carefully done, it is possible to break
the 100 lpmm "barrier." I believe the limits for the very best lenses (in
resolving power) are at about 120 lpmm with some specific lenses at
specific apertures capable of achieving perhaps 140 lpmm representing the
BOB (best of the best, or World Class). Someone else posted remarks about
seeing Shaw prints of magnificent size and extraordinary resolution. Shaw
clearly understood how to extract the very best out of his equipment and
film. While an overall image may not be able to produce this (from lack of
sufficient contrast) regions with sharply defined high contrast edges
will. Although an entire film frame may not deliver this level in a
practical photograph (averaging above the 100 lpmm barrier), done properly
it allows the optics and film system to "rise to the occasion" when
contrast and edge sharpness provide the opportunity.
-- John
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