Re: [Leica] Incident light: A Question & More

[Martin Howard <howard.390@osu.edu>]

Arthur Leyenberger wrote:
> 
> 2) regarding incident readings - Is it true, even with
> incident readings, that you still have to open up with
> lighter objcts and close down with darker objects? 

The quick answer: No.

The long answer: An incident metering is essentially the same as taking
a reflective metering off an 18% grey card held in the light that you're
holding the incident meter.  If the two are correctly calibrated, they
should show the same.

What does this mean?  In practical terms, to use an incident meter, you
hold it in the light you wish to meter, and press the metering button.
Then transfer the shutter speed and f/stop combination to the camera and
shoot away.  Anything in that light which is 18% grey will be rendered as
a mid-grey tone in your negative.  Anything lighter will be lighter, and
darker tones will be darker.

By now, you'll have noticed two things.  The first is the careful use of
the phrase "in the light".  The other is that this only deals with how light
metering affects the appearence of the negative, not development. 

Yep, you can measure different kinds of light with an incident meter.  You
can point the dome directly at a light source, so that the whole dome is
lit.  Or, conversly, you can turn the entire dome away from the light so
that is completely in shadow and measure that light.  Or, you can go half-
way and have the dome half in light, have in shade.  All three will give
different readings.

Development also affects how the (highlights on the) negative appear.  Using
the classic Zone method, you *reflectively* measure the shadow tones to
determine exposure, then *reflectively* measure highlight tones to determine
development.

With an incident meter, the procedure is slightly different.  There are
basically two ways: The quick-and-dirty, or the slightly-less-quick-but-
still-pretty-dirty methods.

Q&D:  Measure the light by placing the dome half in light, half in shade.
The light source doesn't have to be exactly the one that your subject is in,
but it should be similar in intensity (otherwise, what's the point of
measuring it, right? ;)  Use this setting on the camera to expose the film.

Then, through trial and error, determine how you should develop the film to
get good tonal range and highlights that aren't burnt out for the kinds of
photographical situations you commonly encounter and where you use this
type of metering.  It works best if the contrast range isn't too large.

SLQbSPD: First, measure the light with the dome in shadow.  This gives
you the camera exposure.  Then, measure the light with the dome fully in
the light.  This gives you a contrast range which you can then use to
determine how you should develop the film.  Again, use experience to
determine which development times correspond to N, N-1, N+1, etc, for the
subjects that you typically encounter.

Why use contrast measurement with an incident meter instead of a reflective
meter?  Because it's quicker.  Rather than having to figure out which tones
you wish to place in which zone, given a particular subject, simply do two
quick measurements and make note of any unusually large or small contrast
range.


The bottom line is this: Incident meters are great for Q&D work.  I carry
a Leica for streetphotography or just taking snaps of the stuff that happens
around me.  I meter light by sticking the dome half in light, half in shadow
and then transfer the reading to the camera.  I use a standard development
time for pretty much all subjects.

What this allows is very rapid working.  Unless I move from vastly different
lighting situations, I just keep the camera set at a particular exposure
and leave it there, making sure that the aperture gives me sufficient dof
and pre-focussing the lens at a certain distance.  The Leica is now a point-
and-shoot camera.  If I move into a dark alley, I might open up the 
aperture a couple of stops (or more likely, adjust the shutter speed).
Tones fall where they may.  When I get home, I run it all through the
standard development.

I don't get Ansel Adams quality, but then I don't take Ansel Adams'
pictures.  I could probably get some more shadow detail and occasionally
a highlight is burnt out, but for the very large majority of the shots,
the technical quality is perfectly acceptible.


Anyway, I hope that this rather long-winded explanation help you decide
which style of metering to use (reflected or incident) and when to use it.

M.

- -- 
Martin Howard                     | 
Visiting Scholar, CSEL, OSU       |    What boots up must come down.
email: howard.390@osu.edu         | 
www: http://mvhoward.i.am/        +---------------------------------------