I've seen discussion of this as a possible exposure factor only with
the combination of both stop-down metering AND a camera that takes an
average reading of the entire focusing screen, rather than a
centerweighted reading. The idea is that lenses that vignette a bit
wide open may cause slight inaccuracies in cameras that meter wide
open and also take a full-frame average reading. Centerweighted
meters give far less weight to the corners of the frame and this
point is probably moot for those cameras.
It's all probably quite insignificant.
Joe
Shel Belinkoff wrote:
Hi Christian,
A couple of reasons. First, a week or so back JCO made the assertion that
by metering thru a lens set at the taking aperture, measuring the actual
light transited rather than having the camera essentially calculate the
exposure, would result in a more accurate, or precise, exposure. I'd like
to see if there's any truth to that, and if there's any practical
difference.
My guess would be that the difference would be so tiny as to be
insignificant. Esp with film since there is so much latitude.
But if you are really interested in testing this, an interesting way
to do this would be to use Mark's trick with the *istD, that is,
mount the lens so that it is not fully locked, to a position such
that the lever that keeps the aperture wide open is not engaged. I
believe he said it was about 1/8 of a turn or so, but check with
him. This is ok for tests like you want to do, but I would not
recommend this for everyday shooting, as the lens is in somewhat of
a precarious situation not fully locked in and could fall off.
Also, I want to compare two similar lenses, one being a Super Tak that can
only be used stopped down on K bodies and the other being a K mount version
of the lens. It would seem that if the metering styles used were the same
(assuming there IS any difference as suggested by JCO), the comparison
between the two lenses may be more accurate.
However, I doubt that I'd want to shoot that way when making regular
photographs.
Oh, there's a third reason: I've just a little too much time on my hands
right now <LOL>
Shel
[Original Message]
From: Christian <[EMAIL PROTECTED]>
> Is there a way to use a K-mount lens on the K, M, or LX bodies with
stop
> down metering instead of having to use open aperture?
Just a silly question, and forgive my ignorance, but why would you want
to?
