Bob Shell wrote:
On Tuesday, September 6, 2005, at 06:33 AM, Dario Bonazza wrote:
What focusing distance do you think most lenses are optimised for?
Except for macro lenses, most lenses are optimized for infinity.
And except for portrait lenses, don't you think?
Your sentence is what the general theory claims. That's what you usually
read on photo books and magazines.
However, is it true? I don't think above statement to be so much supported
by evidence.
Provided that proper focus is achieved, I can hardly remember a lens whose
performance is truly disappointing at distances of a few inches to a few
meters. On the contrary, few lenses are truly satisfying when focused at
infinity.
I suspect that since most modern lenses are zooms, and since most zooms have
portrait focal lengths in their range and either close-up or macro settings,
lens designers no longer tend to optimize them at infinity (as they probably
did 30 years ago).
Of course, I don't think we have to take this for granted for any lens.
However, I think this can be the case for most Pentax zoom lenses designed
in the last 25 years or so.
Among the prime lenses, once you leave apart the macros, the portrait lenses
and maybe the 50mm (also performing very well at close distance), there's
not so much left below 300mm: just a few Pentax prime lenses below 85mm are
modern designs (20A/FA, 28FA, 31LTD, 35/2FA, 43LTD).
Dario
