At 04:54 10/5/00 , Lex Jenkins wrote:
>As I review the test results on Gary Reese's site I note that many, if not
>most, wide angles and short zooms demonstrated measurable distortion -
>usually barrel, sometimes waveform.
>
>Here's the question: short of repeating Gary's tests, can such distortion be
>reliably detected through the viewfinder? If so, this would certainly
>simplify shopping.
[remainder snipped off]
The answer is yes and no. It depends on what you are aiming at, and I
think you've got the right idea.
Certainly, chromatic aberration is all but impossible to detect through the
viewfinder. It shows in magnified large prints or projected
transparencies. You can detect moderate barrel or pincushion, if it's the
right subject material and even easier if you tripod the camera. The
secret is the right subject material.
You wouldn't know if there was any barrel or pincushion in photographs such
as these:
http://johnlind.tripod.com/indexphoto.html
http://johnlind.tripod.com/oly/gallery/om61.html
http://johnlind.tripod.com/oly/gallery/om73.html
You could if there was any in architecturals with strong rectilinear lines
such as these. The last one would have been easy for spotting barrel or
pincushion as I remember painfully having to hand hold the shift lens for
it. The slightest bit off from a horizontal lens axis or vertical base
plate showed dramatically in the edges of the viewfinder:
http://johnlind.tripod.com/oly/gallery/om65.html
http://johnlind.tripod.com/oly/gallery/om66.html
http://johnlind.tripod.com/oly/gallery/om67.html
http://johnlind.tripod.com/oly/gallery/om68.html
Alas, I don't have a good example to show you of barrel or pincushion. The
ultimate barrel "distortion" is this:
http://johnlind.tripod.com/science/sciencelens.html#Spherical
However, I think it's *supposed* to look that way.
-- John
< 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 >
|