Wayne Harridge wrote:
>
> 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).
>
I've added the rear bellows standard adjustment alternative to the table:
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 Adj.
Bellows
Repro Magni- Image ----------- ------------ Change
------------ Change
Ratio fication Size Size %chg. Size %chg. Ratio
Size %chg. Ratio
1:10 0.10 2.5 2.4 -4% 2.2 -13% 3.0
2.4 -05% 1.1
1:5 0.20 5.0 4.6 -8% 3.8 -24% 3.1 4.5
-09% 1.2
1:2 0.50 12.5 10.7 -14% 6.7 -46% 3.2 10.0
-20% 1.4
1:1 1.00 25.0 20.0 -20% 7.8 -69% 3.4 16.7
-33% 1.7
Moving the entire camera without changing the focus is still the best
alternative. Fortunately, it's also far the easiest, as it doesn't
involve the refocusing required by the other two.
-------------------------------------------------
And I've done the calculations for a 135mm lens.
Calculated for a 135mm lens, here are the changes in magnification
resulting from adding about one inch, 25mm, to the focal distance:
Move Camera Refocus Adj.
Bellows
Repro Magni- Image ----------- ------------ Change
------------ Change
Ratio fication Size Size %chg. Size %chg. Ratio
Size %chg. Ratio
1:10 0.10 2.5 2.5 -2% 2.2 -11% 6.5
2.5 -02% 1.1
1:5 0.20 5.0 4.9 -3% 4.0 -20% 6.6
4.8 -04% 1.2
1:2 0.50 12.5 11.8 -6% 7.4 -41% 7.1
11.4 -08% 1.5
1:1 1.00 25.0 22.9 -8% 8.8 -65% 7.6
21.1 -16% 1.8
The longer lens does indeed make for less magnification change.
-------------------------------------------------
This is all in a spreadsheet, so alternative focal lengths and focal
plane changes may be calculated quickly. Not instantly, as there are
four values that have to be calculated by goal seeking iteration.
A. Calculating Moose
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