Re: Matching lenses - distortion

[erker@xxxxxxxxxxxxxx (Greg Erker)]

>Your method sounds great to me - for the purposes
>you intended, it is simpler than my chart, that's
>for sure.  8-)  I spent a long time getting it
>just right.

  As well as my 8 dots I was thinking of
putting some fine parallell lines near
the center. I was thinking this would
aid me in getting the focus at it's best
possible point on the first lens.

  I would then mark the distance and
just test all the other lenses from exactly
the same distance.

  Back in my insomnia days I found that
the Rikenon (tessars) lenses aren't perfectly
flat field so one has to choose whether
to have the center or the edges in focus
when projecting the flat test slide on
a flat wall. Focusing with the center seems
easiest.

  The corner dots aren't terribly out of
focus, so I think it should be easy to
mark the center of the dot to within 1mm.
If the projected diagonal is 1 metre then
the measurement is accurate to +/- 0.2%.

Greg