RolandRB wrote:


So at full aperture of f2.8 the film distance has to be accurate to
within a third of a millimeter. That would take some very careful
adjustment on your part. If you have adjusting screws then once you
"get it right" and then tighten the screws (if that is what you have
to do) then the very act of tightening them might shift the distance
by that amount and throw it out again.

When I last did it I adjusted the three screws a quarter of a turn at a
time, being careful that all were turned the same amount and checking that
I had focus over the whole screen.

There is no locking mechanism on the adjusting screws. They are reasonably
stiff to turn and with the new foam in the screen holder there is a fair
bit of pressure on them so, as I don't change screens, little reason to
suspect that they rotate.

The more I write the more urgent I feel the need is to check them for piece
of mind with the more usual lenses. Also ought to go out with a tripod and
see what I get at f22.

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