[Leica] Re: Incident Metering - resources needed

[Brougham <brougham3@yahoo.com>]

"Simon Lamb" <simon@sclamb.com> wrote:

> Why is the real issue knowing how much light the subject is
> reflecting?  The whole point of incident metering is you dispense
with
> vagaries of the meter et al.  It doesn't matter how much light the
> subject is absorbing as long as you know how much is falling on it.

Maybe I can add a few helpful observations to what Mark already wrote.

The film doesn't *care* about the light falling on the subject.  The
film only cares about the light reflected off the subject, through the
lens, and falling onto the film itself.  In most cases, an incident
meter will be plenty.

Consider some extreme examples...

A light bulb that is turned on in an otherwise-dark room (but not a
darkroom.)  If you meter the light falling *on* the bulb, you're going
to overexpose.

A blackhole that sucks all available light into it located in your
backyard, on a nice sunny day (so you can use the sunny 16 rule.)
Meter the light falling *on* the blackhole, assume that's the same as
that reflected back, and you're going to seriously underexpose said
blackhole.

Back to a more realistic example...  For the same light falling on a
subject, dull red velvet will reflect far less light back into the
lens than a shiny car painted the same hue of red.  If you want to
render both reds to be the same, they will need different exposures
even if the ambient light is the same.



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