Archived posting to the Leica Users Group, 2000/08/24

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Subject: Re: [Leica] white dot and metering
From: "Dan Post" <>
Date: Thu, 24 Aug 2000 09:24:43 -0700
References: <>

Curious Dan- Here, let me get the smilies out of the way! :o)  :o) :o) :o)
:o)- insert where needed!
Well- I have a sneaky suspicion that the area of the curtain measured by the
M6 TTL and any other M6 is the average of the white dot and a certain area
of black curtain around it- my dot isn't 'pure' white, either, but has a
textured appearance.
Insofar as a scene measuring 18% or 13%- Years ago when I started to learn
photography, film was rated with a speed that gave the "minimum exposure
necessary for adequate shadow detail...." according to the little 'dope'
sheet that came with the film. Perhaps the 5% extra was a fudge factor! This
would assure that if you metered off a gray card that the shadows would be
adequately exposed even if there was a slight error in the meter reading....
remember, back then, we didn't have meters accurate to 1/100 of a stop, and
we didn't worry about such tedious details! :o)
They recalculated the so called 'speed point' of films later- and now the
exposure guides, or ISO actually reflect a calculated exposure that places
the shadow further up the 'toe' of the response curve.
My feeling- and I get this "IT AIN"T EXACTLY AS IT APPEARS" feeling since I
learned electronics in the Navy, and learned that the very expensive
equipment I worked on had resistors and capacitors with tolerances of 1%, 5%
and even 10%! I am sure that the extra 5%, if true, is a safety factor. It
arssures an adequate exposure for those who don't take the time to shoot a
roll, develop, then read the film with a densitometer to see what their
exposure index should be with that film/meter/camera combination--- I've
done that- it's neat to know what the actual EI is, but it's a tedious pain
in the ass when you can give a little fudge factor to the mix, go out and
shoot pictures without picking the fly spots out of the pepper! I used to be
anal retentive, but 10 years on Prozac pretty much got me back to enjoying
taking pictures, and not getting toooooo wrapped up in the minutiae!
HAve fun! Trust your meter! BE happy! Eat butter! One white bread toast! Tou
only come around once, and it your photos look good, do sweat it!
Dan ( The other, really crazy one!) Post
- ----- Original Message -----
From: "Dan Honemann" <>
To: <>
Sent: Wednesday, August 23, 2000 10:59 AM
Subject: [Leica] white dot and metering

> Ok, here's a dumb question (so those of you who have low tolerance for
> questions can skip to the next msg now).  The M6 TTL meters off of a white
> dot on the shutter curtain.  Why isn't the dot 18% grey?  Does the meter
> test light reflected off both the white dot and some of the black curtain
> that the composite represents grey?
> I'm assuming the meter works by comparing the reflected light through the
> lens to the light reflected off the white dot.
> And why do we use 18% grey cards anyway when "scientific studies now
> indicate that an average scene actually reflects 13% (not 18%) of the
> that falls on it" (Peter Burian, _National Geographic Photography Field
> Guide_, p.137)?
> Curious Dan

Replies: Reply from Ted Grant <> (Re: [Leica] white dot and metering)
In reply to: Message from "Dan Honemann" <> ([Leica] white dot and metering)