Thanks for that Moose, not really intuitive so doing the maths was a
sensible step.
...Wayne
>
> 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
>
> ==============================================
> List usage info: http://www.zuikoholic.com
> List nannies: olympusadmin@xxxxxxxxxx
> ==============================================
>
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|