Graydon wrote:
On Tue, May 19, 2009 at 04:16:17PM +0100, mike wilson scripsit:
---- Graydon <o...@uniserve.com> wrote:
[gunch]
Because the screwdriver is there on the adapter, but there's nothing in
the lens to adjust. I don't want the camera body trying to turn
something it can't to find out if anything adjusts.
And yes I could set the camera body to MF before mounting the lens, but
forgetting should not have dire mechanical consequences.
It doesn't. I use M series lenses all the time on my DL2, leaving AF on so
that I can use focus confrim and trap focus. Been doing that for just over
three years and for another mumblemumble years with my Z1-p. I cannot see any
marks on my lens mounts at all.
With the Adaptall 2 adaptor, there's a lens, and then a mount-specific
adaptor. If the lens is pure MF, and the adaptor -- because that's what
one can get off ebay -- supports auto-focus, the camera has absolutely
no way to tell that the screw drive isn't connected to anything.
That's the unusual edge case. I don't imagine the problem would arise
with a Pentax M lens.
The Adaptall Kmount adaptors replicate either K/M or A lenses. I don't
think there are _any_ autofocus ones, never mind Kmount ones. I use my
Tamron 300/2.8, 90/2.5 and 70-210 zoom on my LX, ME Super, Z1-p and DL2
with no problems whatsoever, using whichever adaptor happens to be
installed at the time. No sign of adaptor damage.
The other part of it is that the camera really, really needs to
know the focal length to auto-focus accurately.
-- Graydon, who has tried to use focus confirm on the 500 while
the camera still thought it was 800.
Not by my understanding of how AF systems work. Is there
something different in the K10/20 systems? What they generally do
need is a decent amount of light.
I think it's connected to the shake reduction.
So far as I can tell in the case of the K20D, autofocus and shake
reduction are really one combined system with different sensor
inputs and mechanical parts, but which meet up in the electronic
controls.
I don't see how the AF system would need to know the FL of a lens to
work. It just measures contrast and stops everything when it is
highest.
AF doesn't, but the shake reduction does, and the autofocus and the
shake reduction talk to each other.
I don't know why, or how; I do know the K20D firmware upgrade that was
supposed to improve anti-shake increased autofocus speed.
I wonder if the antishake confuses the AF by reducing apparent contrast
unless the correct FL is known, thereby allowing some software cludge.
--
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