Gary has just provided me with an explanation of the tests, see below:
> Gary Reese <pcacala@xxxxxxxxxxxxx> wrote:
>
> Hi Wayne:
>
> << Why should there be any difference in vignetting and distortion
> using
> different OM
> bodies ? Was the same lens used for both of these tests ? >>
>
> Best I recall, it was two different lenses tested about two years
> apart,
> since I used an OM-1 in the first few months of testing and an
> OM-2000
> about two years into it. Someone on the list probably recalls mailing
> the 400mm to me early on - could have been anyone of about 13 owners
> who
> supplied lenses early on via the mail. The second was likely
> supplied
> locally, or by someone who drove in equipment for a test session. I
> probably did that one along with the 400mm f/4 Tamron and the first
> Novoflex tests. Without reevaluating the slides, both could have had
> equal vignetting at A-. I just never established a set of reference
> slides for A, A-, B+, B, B-, etc. the way I did for "SQF" grades.
> They
> are subjective and relative grades, not objective and absolute. Two
> observers would probably argue over 1/3 grade differences, but a full
> grade would be obvious to all. The exact grade would also be
> arguable,
> but because I did all the grading, that variable was more or less
> held
> constant. Also, I had to set up and take down the lighting from
> session
> to session, so evenness of illumination could have varied from one
> test
> to the next, even though I usually balanced corner readings with an
> incident light meter.
>
> Feel free to post the response.
>
> Gary Reese
> Las Vegas, NV
Wayne Harridge
http://members.optusnet.com.au/~w_harridge
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