At 22:54 1/28/01, Acer V asked:
if i have a t32 sitting on top of a 1n and use the 50/3.5mac, will the
flash cover subject? all the way till 1:2 or approx how far? is the
aperture cals just like gn/distance or is there some other loss from lens
extension?
Acer,
First, if you didn't know this about the T-32:
You can tilt the flash tube 15 degrees downward by first tilting the tube
straight up, then moving a slider under it completely to the right, then
tilting the tube down again. This opens up a slot that allows the tube to
tilt downward.
The danger in shoe mounted flash with a macro that close is the lens
blocking the light from the flash. Someone who has used the 50/3.5 can
tell you how close you can get before you need to move the flash from the shoe.
Since the OM-1n uses the T-32 in Normal Auto (versus TTL Auto) I believe
you will have to compute the extension factor to adjust the aperture at
distances less than about 40cm, or about 16 inches. The heuristic ("rule
of thumb") taking the extension factor into account is a subject distance
less than eight times the focal length. For methods on how to compute
this, see my web site, under the "Science of Photography" in the "Exposure"
section, "Macrophotography" sub-section. If my thinking is straight, you
will want to set the T-32 in Normal Auto for an aperture that will give you
the proper distance range, and then open up the from that on the lens using
the extension factor. As I mention in my discussion of this, an
OM-2[n,S,sp] or OM-4[T,ti] in Auto with the T-32 in TTL Auto will
automagically compensate.
Web Site:
http://johnlind.tripod.com/
Direct link to computing extension/bellows factors:
http://johnlind.tripod.com/science/scienceexposure.html#Macrophotography
One additional piece of information that might help with the equations:
M = x/f
M = Magnification
x = lens extension
f = focal length
Therefore, if you know the magnification, you can find
the lens extension from it and the focal length:
x = M * f
I need to add this to that portion of my web site.
-- John
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