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[OM] Re: Thoughts on IS - and a Confession.

Subject: [OM] Re: Thoughts on IS - and a Confession.
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Sat, 07 Aug 2004 22:45:51 -0700
Carlos J. Santisteban Salinas wrote:

>Unlike the Zuiko lenses, most mounts are designed to keep the lens
>stopped-down up to the selected f-stop (on the aperture ring). When mounted
>on the camera, these lenses' auto-iris pin is pressed to keep the lens wide
>open while focusing and/or metering, and the camera will release the pin
>while taking the picture. Just the opposite of the OM -- lens keeps
>wide-open *until* the body moves the auto-iris lever when firing.
>
>Mountless Tamron Adaptall lenses behave in a similar way to Zuikos. Another
>exception to the general rule are M42 auto diaphragm lenses (see below).
>And Can*n FD lenses are the weirdest thing on earth, regarding to coupling
>;-)
>
Well, those 3 types of mounts are the only ones I have used, except on 
very rare occasion, in years. I had forgotten that about Nik*n, but see 
that it is so when I drag one out and look.

>>>From: Peter Klein <pklein@xxxxxxxxxx>
>>>
>>>The Pentax *ist D meters with MF M42 and "K"
>>>lenses with a single button push.  Pentax released a firmware upgrade that
>>>stops the lens down when you push the "green button," meters, and then
>>>opens up again.  It also stops down for shooting.  So you get an aperture
>>>priority mode with one-touch metering........................
>>>
>>>Obligatory OM content:  Unfortunately, the *ist does not take MF
>>>Zuikos.  If it did, I'd buy it in a heartbeat.  And if the E-1 treated MF
>>>Zuikos as the *ist does legacy Pentax lenses, I'd buy *it* in a heartbeat,
>>>too.
>>>      
>>>
>
>Please note that M42 lenses can be mounted on the *ist via the usual M42-K
>adapter, and the new firmware may meter with them, but the auto-diaphragm
>action of the MF Pent*x-K bajonett lenses is lost. In fact, 'auto-only' M42
>lenses (those without the Auto/Man switch) would work wide-open *only*,
>because the M42-K adapter doesn't press the auto iris pin.
>
So Peter is right about K-mount, but not about M42?

>I once tried to take a pic of a car in a garage with the 300D (AF lens and
>flash, which also acts as AF assist light). The garage was in near total
>darkness because lighting was broken -- fortunately someone put a bit of
>fluorescent paint on each column!
>
>...No way to focus, no matter how many times I tried, in different angles
>and with the AF assist flashing as mad. Manual focusing was obviously
>impossible, thus no pic was taken :-(
>
I just tried this and got a similar result. I could easily take pics of 
anything in the dark garage with quick and easy AF lock. The car is a 
convertible with the top down and I was also unable to get AF of the 
interior unless I was well clear of the windows, then it worked fine. A 
shot of the back of the car worked with the folded top and mechanism in 
a good part of the frame, otherwise not. I suggest that the problem is 
the nature of the subject, with the specular reflections off shiny body 
and glass surfaces confusing the AF.




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