> > Anyway: for various example magnifications at f22 with object distance
> > adjusted for equal magnification ... compare the differences in DOF
> > for a 500mm and 20 mm lens ...
> >
> > M 500mm 20mm
> > 5:1 0.2640 0.2643
> > 1:1 2.200 2.207
> > 1:5 33.001 33.924
> > 1:20 462.247 693.180
>At 1:50, about the magnification of a full body shot in vertical format,
>the corresponding line would read:
>
>M 500mm 20mm
>1:50 2813.511mm infinite (0.43m to infinity)
An additional question:
First an example (as someone wrote already):
1) Put two books standing so that:
- book A is on the left side of the picture and in focus
- book B is on the right side of the picture in the background
2) Take two shots with the same magnification of book A,
one with a 20mm lens and another with a 500mm lens,
both using the same aperture (f-value). Focus in book A.
According to the previous messages the DOF in the 20mm shot
is greater (it shouldn't matter but I have e.g. a 1:20 shot
in my mind).
In the 20mm shot the background book B fills smaller part of
the film because the angle of view is bigger.
Is it so that if we magnify the *background* book B of the 20mm
shot so that it is the same size as in the 500mm shot then they
are equally unsharp?
We must of course assume that other components (e.g. film and
lens) are ideal so we can magnify any amount without problems
with resolution etc.
Any sense here?
Vesa
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