"Alexandre A. P. Suaide" wrote:
>
> Hello,
>
> I have only KA lenses and I was thinking to buy one K lens but
> first I would like to know how it works on the PZ-1P. Let me explain
> better. the KA lenses works wide open because the electronic contacts
> tell the camera which aperture was set in the lens. I don't need to close
> the diaphragm to meter the light. for K lenses, do I need to close the
> diaphragm (press DOF button) while adjusting the shutter speed to have
> the correct exposure?
You've got a fundamental misunderstanding here. K lenses, just like
KA lenses, meter wide open because a mechanical linkage tells the
camera body how much the lens has been stopped down (and thus how
much less light will be entering the camera at the taking aperture).
Let's consider an example:
The exposure metering system doesn't need to know whether the lens
is an f5.6 lens that will be stopping down to f11, or an f1.4 lens
that will stop down to f2.8 - all it needs to know is that the final
exposure will be made with only one quarter of the light currently
falling on the metering sensors.
The electronic contacts tell the body what the maximum aperture is,
which is useful for viewfinder display of the aperture. But most
Pentax cameras use the mechanical linkage between the lens and the
body to control the metering circuits. The electronic contacts
aren't needed, in general, for exposure metering.
The exception is the two bodies (the MZ-50, and the MZ-30) which
don't use the mechanical link. That's why these bodies don't work
with pre-"A"-series lenses.
Refer to Boz's K-mount page for more details on all this stuff.
--
John Francis [EMAIL PROTECTED] Silicon Graphics, Inc.
(650)933-8295 2011 N. Shoreline Blvd. MS 43U-991
(650)932-0828 (Fax) Mountain View, CA 94043-1389
Hello. My name is Darth Vader. I am your father. Prepare to die.
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