Re: [Leica] Consistent underexposure problem

["Anthony Atkielski" <anthony@atkielski.com>]

From: Godfrey DiGiorgi <ramarren@bayarea.net>
Sent: Saturday, September 18, 1999 19:31
Subject: Re: [Leica] Consistent underexposure problem


> When I worked at JPL/NASA, it was unthinkable that we
> would buy a half-million dollar scope and not test,
> calibrate it before use. Why should a camera, even a
> $3000 camera, be any different?

Some products are designed with the assumption that the user will calibrate
himself, others are designed with the assumption that the user will calibrate
the device.  In the latter case, a trip back to the service center is not
necessary for calibration.  The fact that cameras do not provide for
user-modifiable calibration implies that they had better be calibrated at the
factory.  It makes no sense to wait for it to be sent back for calibration when
this can be accomplished more quickly, more accurately, and at lower cost by
just improving quality control during manufacture.

> As I said, I don't expect it to be off.

I got a Minolta spot meter and tested the meter, my M6, my F5, and my FG against
a gray card.  All agreed to within 1/10 stop, except for the Nikon FG, which was
off by half a stop or so.

> That's one reason for running a reference test against
> a known-accurate meter ...

So how do I find a known-accurate meter?  I bought a spot meter today, but since
I have nothing to test it against except other meters of unknown accuracy, I
cannot say that it is known to be accurate.

I did see that three different meters agreed in my tests, which to me is strong
circumstantial evidence that they are all accurate.

> I'm perhaps overly cautious: I like to test that equipment
> is functioning to my expectations before I start working
> on what I'm done wrong. Part of my engineering background.

I have an engineering background, too, but when I spent vast amounts of my
hard-earned salary for nice equipment, I expect that part of what I spend will
have gone to paying for the necessary quality control up front.  Why should I
spend additional time and money doing the manufacturer's job?  If he is too lazy
or cheap to get it right even when his customers are spending top dollar on his
equipment, maybe some other vendor deserves the business.

Logically, you should also check the shutter speed and movement in the camera,
and the resolution of each lens.  Do you?

> Don't sweat it, I fully expect that you'll find the meter
> to be right on the money if you test it.

My semi-rigorous tests today appear to show that the meter is indeed completely
accurate (at least to within the tolerances required for normal
photography--1/10 of a stop isn't much!).

> Gossen, Sekonic, Minolta and Calculite, amongst others,
> manufacture an excellent range of meters.

I ended up with a Minolta that I got on the way home today.  It was the only
spot meter available at my favorite photo store.  I wanted a spot meter because
I'm so rarely within a convenient distance of my subject (towers, buildings,
etc.), and because it seemed logical to meter what the camera will actually see,
rather than the light falling in the vicinity of the subject.

At least you mentioned Minolta, which reassures me.  I've never cared for their
cameras (but never used them, either), but perhaps their meters are pretty good.
It was expensive, so I hope I didn't get shafted.

> An incident light meter is harder to fool because it
> measures the light falling on it and gives an exposure
> reading which is calibrated to reproduce that 18% gray
> target accurately in that amount of incident light.

Ah... that makes sense!  I was wondering what the advantage was supposed to be.

The only problem is that almost none of my subjects are close enough to make use
of an incident meter practical.  I also don't see how they account for the
distance between the camera and the subject.

Unfortunately, the spot meter cost more than I could really afford, so getting
an incident meter as well is not an option at this time (I don't want to give up
the spot meter).

Of course, with the F5 and the Leica (once I get used to the latter, I hope), I
should not need any external meters, anyway.

  -- Anthony