Fernando,
I think I recall that thread.
If I am remembering correcting it was an issue with a 500mm f8 mirror lens in
comparison to a shorter lens (can't remember that one I am afraid).
The issue was resolved that the angle of spot reading varies with focal length.
With a 50mm IIRC it is 2 degree. With the 500mm I think Skip figured it to be
less than 0.5 of a degree. Therefore if you use a wider than 50mm lens you will
get a slightly wider spot reading.
This leads to a very specific spot reading with longer lenses if you make a
comparison of the same site with more than one lens.
I would imagine that it would be easier to think in terms of the metering your
scene requires rather than getting the same result from test card. Its nice to
know the meter is working and consistent. I believe that when calibrating a
meter a standard lens would be part of the base line measurements.
I hope this helps some, I am sure I have left some stuff out. Perhaps a browse
through the archives for the original post might offer some stuff I forgot.
Dan S.
From: Fernando Gonzalez Gentile <fgnzalez@xxxxxxxxxxxxx>
> This reminds me of a post sent on Thu, 13 Feb 2003 00:10:34 +0200.
> During those days I was offlist and was surprised to find it at
> the website.
> It doesn't concern me directly since I won't ever own a 4 because
> it is not
> serviceable in my country.
> But I'm amazed to find in this post extensive documented data on spot
> metering vs. CW metering on the same recently CLA'd 4 body - CW was
> consistent though a large array of lenses but spot was offset by
> differentvalues on different lenses, reading the same eavenly lit
> surface. It was a
> significant offset and showed on slides, more obviously when using
> lensesthat caused a more significant offset.
> The thread didn't last long, and John commented '...get used to
> it...'.Is this a characteristic metering behaviour of the 4(T-Ti)
> and 2SP, or is it
> that when behaving this way it is imposible to adjust/repair
> (circuit?)What about the 3 (T-Ti) ?
> Or is it due to each lens design, or the way it tells its aperture
> to the
> body ?
>
> As another listee used to state: "inquiring minds want to know".
>
> Fernando
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