On Oct 11, 2005, at 7:40 PM, Tom Reese wrote:
I think you get more magnification if you put the camera ->
converter ->
tubes -> lens
if you do the math and assume 50mm of extension:
your way is equivalent to a 100mm lens with 50mm of extension yielding
something like 1:2 magnification (half life size)
the other way is equivalent to a 50mm lens with 50mm of extension
yielding
1:1 magnification then doubled by converter to 2:1 magnification
(twice life
size).
that is with the lens focused to infinity. the magnification
changes when
you have it focused closer but the general formulas still pretty
much hold
up.
Your way would give you much more working distance.
Thanks for your reply, Tom.
Being an empiricist first and a mathematician second, I fitted the
setup using the A50 Macro racked out to maximum extension both ways
and took a reading off my steel ruler:
camera->converter->tubes->lens netted 14.1mm horizontal field of view
for a 1.7:1 magnification
camera->tubes->converter->lens netted 12.4mm horizontal field of view
for a 1.9:1 magnification
The working distance at maximum magnification was very little
different, but I didn't measure it. This is for 'flat art' copy work
on a light table, so working distance isn't much of an issue. :-)
Godfrey
