The announcement that the new Oly 90 mm macro is now official vaporware spurred
more interest in higher mag macro. No one has taken over where Chuck left off
on estimating working distance, but I did find his post. So the "effective
fov" is about 180 mm FF equivalent but is the working distance anywhere close
to that? Chuck said no. Just to get a very rough idea about working
distance, will assume MFT needs to achieve 1:2 mag for 1:1 FF equivalent
magnification. Now the mag purists will get out their knifes as mag doesn't
really change as is a f(image vs object size) and MFT is just a crop, but even
Oly surrendered on that and calls it FF equivalent mag. Now assuming a thin
lens at 1:2, MFT the object distance is 3X FL so 90X3=270mm. A 180mm lens at
1:1 on FF will have an object distance at 180 X2= 360mm. So FF at 180mm will
have much better working distance and the MFT for working distance
considerations could be thought more like a 135mm lens on FF, if at other mags
this re
lationship holds. It is much more complicated as the lenses are complex, not
symmetrical and have focal length shortening at higher mags, and these
distances are not to the front of the lens, but the new 90mm is not likely at
1:1 to have enough working distance for some critters.
On the other hand, it effectively goes to 4:1 mag if the announcements are
true. The OM lenses that achieve this mag are much much shorter and Dean might
really like this lens as a result. I hope we'll find out what the working
distances are at higher mags.
On another note, I partially viewed an Oly sponsored video on STF-8 macro flash
and was disconcerted to learn that TTL function does not work in focus
bracketing mode. The Oly cam manuals
have flash instructions for this mode but the STF-8 manual doesn't explicitly
say this, but TTL option is greyed out in bracketing mode. It will work in
manual mode but accurate fill flash with bracketing isn't that easy. Very
strange decision and a well-hidden deficit, IMO. I wish Oly updated a cross
polarization option too.
I think the LED option is looking better for focus bracketing of critters.
Need to reinvestigate that. The FF twin macro flash options will work but have
their problems too.
Macro muser, Mike
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