Olympus-OM
[Top] [All Lists]

[OM] Re: Focus stacking

Subject: [OM] Re: Focus stacking
From: Moose <olymoose@xxxxxxxxx>
Date: Thu, 01 May 2008 02:54:14 -0700
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.
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


==============================================
List usage info:     http://www.zuikoholic.com
List nannies:        olympusadmin@xxxxxxxxxx
==============================================

<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz