On Sep 13, 2010, at 3:02 PM, John Francis wrote:
I believe the issues surfaced when using lenses with a large maximum
aperture (such as a 50mm/f1.4).
Although Pentax never explained exactly what was happening, the most
plausible hypothesis I saw was that the exposure metering in the K10D
(and, I would assume, in later cameras) had some sort of compensation
curve for the metering system based on the maximum aperture of the
lens
(presumably because of known problems with light hitting sensors at an
oblique angle). An 'M' lens does not communicate maximum aperture (or
the aperture to be used) to the body, so the exposure correction would
not be performed (or would be performed using one fixed value for all
'M' lenses at any aperture).
I didn't pay too much attention to the issue, because I decided to go
with 'A' or later lenses back in '95 when I got my PZ-1p, so I rarely
put an 'M' lens on any of my later bodies. And, in any case, I don't
assume the metering on any DSLR is going to give me as good control of
the exposure as I can get by looking at the histogram.
The "green button" metering technique should get you close; just be
prepared to apply some exposure compensation if you want it spot-on.
That was necessary (at least with the *ist-D and K10D) anyway; from
what Paul Stenquist says the K-7 may do rather better in this regard.
I've shot a bit with a K 85/1.8 on the K7, but haven't used it
extensively and don't recall how successful those attempts were. I'll
have to give it a try and see how it does wide open and at a small ap.
Paul
On Mon, Sep 13, 2010 at 08:35:49PM +0200, Jens wrote:
I may be using my M lenses too little. But I have never noticed any
exposure problems - except for those caused by the well known "slow
aperture syndrom", occuring when lenses are left unused for too
long - or stored with open aperture blades (on a camera or
otherwise).
I use a Seikanon wide angle macro lens quite often - which works
like an M lens. It's an absolutely brilliant lens - which I believe
is made by a company related to the later so well known Seiko
brand. No exposure problems, that I know of. Razor sharp.
Regards
Jens
--
Treat others as you would like to be treated yourself.
On Sep 13, 2010 19:02 "Steven Desjardins" <[email protected]> wrote:
I've never really used an M lens on a Pentax digital, but I'm
thinking
about buying one. I know the green button trick, but how well
does it
actually work? Metering OK and all that?
--
Steve Desjardins
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