In a message dated 8/29/2003 9:22:41 AM Eastern Daylight Time, fred42@xxxxxxxxx
writes:
> Is it possible to figure out what that position of the lever is?
>
> Having compared my 50mm/f1.8 and 135/f3.5 at the same aperture (f8) the tab
> on the lens is not in the same position. So from that would I be correct in
> guessing that the position of the tab will be different based on the focal
> length of the lens? Even when comparing same apertures? So to find the
> correct position for the lever one must look at the same focal length auto
> lens?
The difference you're seeing comes from the fact that the two lenses have
different maximum apertures, not from their differing focal lengths. This is
because the position of the lever is used to communicate to the camera how much
you've stopped down from wide open. It doesn't communicate actual aperture
(which is why our Oly's can't display the aperture in the viewfinder). All
lenses should have the lever in the same position when they're wide open - so
if your 50/1.8 is set to 1.8 and your 135/3.5 is set to 3.5, the two levers
should be in the same position. If they are both set at f/8, then the 50/1.8 is
stopped down about 5-1/3 stops, but the 135/3.5 is stopped down only about
2-1/2 stops, so the levers should be in a different position.
> Given the above what sort of success would one likely have with a t-mount
> adapter and a selection of different focal length and speed
> lenses?
The T-mount should have a fixed pin set to communicate "fully open" to the
body. I understand that on some T-mounts the lever position is adjustable, so
you might need to do some trial-and-error. Use one of your Zuikos, set
wide-open, for comparison.
Hope this helps,
Paul Schings
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