Moose's observation that moving the camera has a lesser effect on
magnification was an interesting and probably quite useful point. On
the more general subject of changing magnification here is how I
responded this morning to the same question posed by Jim Brokaw on the
Kiron user's list on Yahoo.
--------------------------------------------------------
I was asked the same magnification question by someone else about moving
the camera to refocus in order to hold the magnification constant. I
said it wouldn't work but had to question myself. So I went back to
review my fundamental optics formulae which states that magnification M
= i/s where i is the distance from the lens to the image (lens to focal
plane) and s is the distance from lens to the subject. So, after taking
the first shot at subject plane #1, if the focus is held constant and
the whole camera and lens assembly is moved, say 10mm closer, then
another part of the object that was 10mm farther away (subject plane #2)
is now in focus and at the same magnification since the distances i and
s have not changed.
However, when the first shot was being made, only the distance from
subject plane #1 was at distance s. The distance to subject plane #2
was at distance s + 10mm. So, as I see it, whether moving the lens or
moving the camera some parts of the image are still at different
magnifications. But it's time to read the CombineZM manual to figure
out how to deal with the problem.
----------------------------------------------------------
For the same reason I don't think your suggestion about refocusing using
a bellow would offer any help. Since magnification is the ratio of
image and object distances if either of them changes the magnification
changes.
But, as I said, I do have to go read the manual which I have avoided
since it's about 4MB. Maybe if lots of images are taken in small steps
by moving the camera only, all of the in-focus bits will be at the same
magnification and, if the software chooses only the in-focus bits then
we end up with a sharp image with all pieces at the same magnification.
Or maybe not. :-)
Chuck Norcutt
Wayne Harridge wrote:
>> Oops, I would also guess that that would also change the
>> image size. Rand E.
>>
>
> Yeah, probably the best approach is to use a longer lens on a bellows and
> refocus on different parts of the subject adjusting the rear bellows
> standard while maintaining the distance from the lens to subject fixed (e.g.
> The Zuiko 135/4.5 macro on the OM Auto Bellows).
>
> OT bit: Would anyone on this list have a Minolta Auto Bellows III they want
> to part with ?
>
> ...Wayne
>
>
>
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