Kostas Kavoussanakis wrote:
On Sun, 5 Feb 2006, mike wilson wrote:
Kostas Kavoussanakis wrote:
The manual states that you may get vignetting if not at infinity. But
the T/C does not have a great focussing range (trade-off for speed),
so some times you are forced to pre-focus (if approximately).
I'm not so sure that it is a tradeoff as much as a need to adhere to
optical rules. But, as you imply and nobody else has mentioned
specifically, it is very fast at focusing.
Ah, misunderstanding, the ambiguity of speed strikes again (though your
statement for AF speed is in agreement with my findings). What I meant
was that in order to have a wider focus range it would have to be a
(say) 2x converter, so as to accommodate more movement. 2x converter=2
stop "loss".
Am I right?
Kostas
Pass. 8-)
My take is that, to be of any use without being too
large/heavy/whatever, Pentax designed it to have limited range of focus.
I'm not sure this would have been influenced by the (nonfocus) speed
of the converter. Possibly both factors come into account. In any
case, this requires the user to prefocus to somewhere near the intended
point. Details are taken care of by the converter, rapidly. My
experience is that the 1.7 focuses at least as fast as the 28-70/2.8,
probably faster.
mike
