In Gary's tests - a most useful collection of data to say the least -
a few lenses had a single vignetting grade of B or C. I could not
understand this, as most of his tests ran something like, "C at f2.0,
A- at f2.8, A thereafter." I posted a question on this list and some-
one responded that Gary had said that this could be explained by
sample variation. I thought this explanation was too simplistic to
be valid. I could not believe that vignetting would be constant
throughout the range of apertures. So I emailed the master himself.
Here is his reply:
"Early on in testing I only determined this grade for a lens at its
wide open aperture. In later testing I determined it at every click
stop until it was gone, or had stabilized. Feel free to post this, if
desired."
Now it all makes sense. If a single grade is displayed, it represents
the worst case vignetting, at a wide open aperture. Unfortunately
we cannot accurately extrapolate this data, but I think it is a safe
bet that the vignetting grade increases at least a little as the aperture
becomes smaller.
Pete
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|