Rand E wrote:
> Oops, I would also guess that that would also change the image size.
>
True, but your instincts are right. I did some calculations. Moving the
camera to shift the plane of focus has much less effect on
magnification, roughly a third as much, as refocusing the lens.
Calculated for a 50mm lens, here are the changes in magnification
resulting from adding about one inch, 25mm to the focal distance:
Move Camera Refocus
Repro Magni- Image ----------- ----------- Change
Ratio fication Size Size %chg. Size %chg. Ratio
1:10 0.10 2.5 2.4 -4% 2.2 -13% 3.0
1:5 0.20 5.0 4.6 -8% 3.8 -24% 3.1
1:2 0.50 12.5 10.7 -14% 6.7 -46% 3.2
1:1 1.00 25.0 20.0 -20% 7.8 -69% 3.4
So that focusing rail is important. Still, the difference even moving
the camera requires compensation. I'd think that's one of the main
requirements of useful software.
I wonder if the one inch increments resulted in magnification
differences that were too large for the software to handle? A focusing
rail would make multiple, much closer images easy. No messing with
focus, just move the rail say a mm or two between shots.
Moose
> Rand E wrote:
>
>> As far as the different magnifications go, I would guess that you would have
>> to focus by moving the camera rather than changing the focus on the lens.
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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