At 05:03 5/20/01, Donald Shedrick wrote (in part):
The results show in all cases the best focus was as
determined by the split image screen at slightly less
than infinity. The difference was clearly seen with a
high quality 12X loupe on the slide.
As a sidelight, I was amazed by the sharpness of all
the lenses at best focus, especially the zooms.
Your method reminds me once again:
1. Proper dioptric correction for those of us who are near/far-sighted is
important to critical focusing. Placing proper correction on the
viewfinders of my OM-1n and OM-2S, and adjusting the OM-4 correctly,
greatly improved the ease with which critical focus is found and set.
2. Taking thoughtful care in where critical focus is placed for an image
can make a huge difference in results. For images with subject(s) having
relatively great depth, best placement of critical focus is often at a
point that allows the depth of field to span the subject depth. As
distance increases the DOF increases faster behind the critical focus point
than in front of it. Thus it may not be best at the center of subject
depth (if the subject is somewhat distant), but a little closer.
Just some related thoughts about all this.
-- John
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