TAKO. INTERNET SEIT 1996.
Olympus-OM

[OM] Re: Focus stacking calculations

Subject: [OM] Re: Focus stacking calculations
From: Moose <olymoose@xxxxxxxxx>
Date: Thu, 01 May 2008 20:16:48 -0700
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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