JS writes:
< Do you have any feeling for the difference between actually changing focus
in
< focus-bracketing, as opposed to changing the camera position?
Moose writes:
<<<This is a classic and unavoidable part of the stacking process, small
differences in magnification need to be corrected. The software expects it.
<<<MikeG should chime in here, as he is more knowledgeable than I. I do know
that moving the camera position has been the preferred method, apparently
creating less to be corrected. I have done it manually, with limited
<<<success. I tend to forget if I have moved the camera between exposures. It
is going to be subject to more fluctuation in not completely static subjects,
changing natural light, etc. than the in-camera focus bracketing of your
<<<E-M1 II, which finishes the stack in a couple of seconds.
My understanding is that is the change in perspective and not magnification
that can cause trouble and artifacts. Most alignment software can deal with
the latter quite well. At low mag, (in general) it is better to use the
focusing ring and approaching 1:1 and higher mag, moving the cam is by far
the best in in this regard, though the alignment software is increasingly good
at dealing with this and even lighting changes. Dr. Focus (long lost 2nd cousin
once removed of Dr. Flash) did confirm this in theory. In between mags,
like focus stacks for orchids, I can confirm that moving the cam on a focusing
rail results in fewer changes in framing, but the alignment software could deal
with either technique equally well except when the wind wreaked havoc on the
framing. The extreme example is "macro landscapes" when one must go from
highish mag to infinity. There an excellent way to obtain a good stack and keep
the perspective constant. This requires one to keep the entrance
pupil stable--putting a wide angle lens on a bellows and moving the rear
standard to change focus is perfect. Jeff Keller came up with a way w/o
mount surgery using a T-mount lens and bellows but I never got it together to
do this.--hope to do so some day if can find the write combo. Any advice on
that appreciated. Moose I think has tried a CU diopter but don't recall if the
result was quite as good.
http://www.heliconsoft.com/forum/viewtopic.php?f=9&t=1141
Using this Franken bellows including mount surgery on an OM Zuiko:
http://www.photomacrography.net/forum/viewtopic.php?t=4879
Keeping things in perspective, Mike
--
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