----- Original Message -----
From: "P�l Jensen" <[EMAIL PROTECTED]>
>Strangely, Zeiss people say that the problem is largest with wide angles
although I can't see why; one should expect it to be wrose with telephotos
due to their smaller DOF or..? I have, however, experienced that the
problems is indeed worse with the 45mm; only once have I seen it with the
120mm.
P�l,
In answer I will quote myself from a previous unrelated thread.
"Wide lenses ..... have very short depth of focus, ie the tolerance for
focussing error at the focal plane. ..... the cone produced by the image
forming light is very wide so that a very, very small change in lens
extension will make the circle of confusion unacceptably large. OTOH a long
lens has a narrow cone of image forming light, and will tolerate a quite
large change in lens extension without exceeding the parameters of
acceptable circles of confusion."
This should clear up a very common misconception.
Regards,
Anthony Farr
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