> 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
There is sense that is often missed by those extolling wide angles for
DOF ... (not getting at you Thomas, honest). So, the image might be
in focus all the way to the horizon, but you could not tell anyway
because it is so small on the film: tiny.
For a "flower and mountains" shot then a prime 20mm lens is certainly
the right tool for the job. If you are after meaningful depth of
field for a group of objects (or even the head and tail of one
subject) than wide angles are a stupid choice.
"Hey, is that spec another lion?"
"Yes, but look how sharp a sec it is ;o)".
If you magnify features in the background of a wide angle shot to be
the same size as features in the background of a telephoto shot the
news is they would hold MUCH less detail .
It is not simple: it is choosing the tool for the job (and for most
of us that means compromises from what we own). IMO for landscape
you choose the spot first and THEN the lens to give the coverage you
want. Ouch ... that comes down in favour of zooms. But the problem
with zooms is it encourages lazy thinking: the spot becomes *here*
and the perspective is dictated by that.
Oh, the fun ... in reality there is no right lens ... the only way is
to look through the viewfinder and see the effect. If it looks right,
chances are it is.
Bob
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