>> They show a man with a incident-light meter -- and he's actually holding it
>> correctly. (I admit, with some embarrassment, that it took me a while to
>> understand that you pointed the dome at the camera, not the light source.)
> And I don't know why you'd be embarassed to admit that you didn't
> understand that at first. I don't think it's exactly obvious at all. Not quite
> as inscrutable as the sequence of button pushes to set sub-mode 6
> of custom function 13 or the reason why you'd ever even want to do so
> but, non-obvious nonetheless.
I'm embarrassed because the instruction manuals specifically state you're
supposed to aim the meter at the camera -- and I was doing it the way _I_
thought was correct. Naughty, naughty.
> You don't point the dome at the camera. With the translucent dome
> fitted over the sensor you point it at the light source to measure
> _incident_ light.
This is true only if you are measuring the intensity of the light source. In
the case of my L-508, it's done by retracting the dome, taking a reading, and
referring to a conversion table.
There is a difference between a light meter and an exposure meter.
> I'm not sure what you might measure by pointing the meter at
> the camera, unless you are photographing the camera ... :-)
You measure the light actually falling on the subject.
If you check the user manual for any incident-light meter, you'll see that it
says to point the dome at the camera.
> From my Gossen Ultra manual (page 17 for those following in your own
> pamphlet):
> "When reading incident light, the spherical diffuser is placed in front of the
> measuring cell window and pointed toward the camera, ie, opposite the subject
> being photographed. The diffuser should receive the same light intensity and
> distribution as that falling on the subject. The reading at this point
> indicates the strength of the light, but does not indicate the light value
> reflected from the subject into the camera lens and onto the film.
It's not supposed to! That's the point of an incident reading -- it's not
affected by subject reflectivity.
> It does indicate the light value that would be reflected into the lens from
> an 18% average reflective subject. Therefore, when working with subjects
> that are primarily very light or very dark, the incident exposure reading
> should be adjusted to compensate for the difference in reflectivity from
> the 18% standard."
Sounds as if the Germans can be just as confused as the Japanese. This is,
like, totally wrong.
The point of incident exposure readings is to render the scene as seen (pun
intended), rather than having the exposure thrown off by "subject failure" --
an average reflectance significantly different from 18%. If a subject is
unusually light or dark, we want it rendered that way -- not under- or
over-exposed.
Of course, no photographic material has an infinitely wide tonal range. If a
scene comprises mostly dark tones, an incident reading might, for some
materials, push the image too close -- or even into -- the toe of the curve.
The photographer might very well decide to increase the exposure (over the
incident reading), then make adjustments in printing. Similarly, he might
decide to slightly reduce the exposure for scenes comprising mostly light tones
when shooting transparency film. But these decisions have NOTHING WHATEVER to
do with subject failure.
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