Re: Bob's Rikenon lens measurements

[Greg Erker <erker@xxxxxxxxxxxxxx>]

>
>lens      | G5.1      B1        B2        B3        B4       B5       G5.2
>----------|-------------------------------------------------------------------
>sum diag  | 1237.5    1230      1228.5    1229.5    1229.5   1244     1240
>rel diags | 0.61%     0.00%     0.12%     0.04%     0.04%    1.14%    0.81%

Hi Bob and other interested parties,

  You seem to have left the minus sign off some of
these relative results. My lens gave a bigger image
than all but B5. B2, B3 and B4 are smaller than the
reference one (B1) so one of these two sets needs
a negative sign.

  If we call a bigger projected image positive. Then
looking at just the diagonals

G5.1 = +0.61% and G5.1 = +0.81% so the average G5
measurement works out as +0.71%

B1 = 0.00% (reference lens)
B2 = -0.12%
B3 = -0.04%
B4 = -0.04%
B5 = +1.14%

and scaling my measurements using Bob's measurement
of G5:

G1 = +0.46%
G2 = +1.00%
G3 = +0.83%
G4 = +1.77%
G5 = +0.71%

---

  So not only do Bob and I have good luck with lenses
but we each bought the correct cameras, since his group
is well matched to itself but not that well matched with mine.
My best 3 lenses (G1 to G3) are well matched (though not as
good as Bob's (B1 to B4).

  I don't thing Bob changing shutters for some of
the measurements should do anything unless the Citizen
shutter is significantly thinner than my Seikosha (unlikely).
A 1 mm difference in thickness would cause a 0.13% change
in those measurements (1 in 760 mm). A 2mm change would affect
them by 0.26%.

  I have loaded some test film into my Stereo 225 and
we'll see how well matched G2 and G3 are in the real
world of taking photos. (The shutter isn't yet linked
so I'll be shooting it like twin cameras).

Greg