Joel Wilcox <jowilcox@xxxxxxxxxxxxxxxxxxx> wrote:
To my question on the extension tubes,
>Tomoko, yes the Vivitar extension tubes are auto, so that if aperture stopdown
is a >culprit in vibration to the lens, these tubes might contribute in some way
to the >problem.
>However, the OM-1 and OM-2S, both of which I used for my test frames of the
>striped orchid with 200/f4 and extension tubs, are quite different in terms of
how their >mirror lockup works vis a vis aperture stop down. There is no way to
prefire the >aperture stop down on the OM-1, even though you can manually lock
up the mirror. >Timer prefire on the OM-2S locks up the mirror as well as stops
down the aperture.
I checked on the aperture prefire of the OM-1 (mine is an M-1). It looks that
if you use the self-timer in addition to MLU, the aperture closes down at about
4 sec prior to the shutter opening.
>The fact that the results with OM-1 and OM-2S were indistinguishable
>suggests to me that the stopdown of the aperture prior to exposure is a
>non-issue.
What is the magnification of a 50mm lens used as a loupe?
When I used my 8x loupe to examine my slides between the two 200mm (f4 & f5)
plus 2XA TC results, I had a hard time distinguishing any differences in some of
my slides. When I projected the slides to 22x33 inches, I was able to discern a
little difference among the slides with respect to the sharpness. (I am not
finished with my evaluation yet, so I don't have anything specific to post yet)
Tomoko Yamamoto
mailto:tomokoy@xxxxxxxxx
http://www.charm.net/~tomokoy/
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