[Leica] Incident light measurement

[Lutz Konermann <lutzkonermann@compuserve.com>]

I just dropped into what seems to be an ongoing exchange of views. I read 
Frank's and Bernard's and thought I could add some...

I've been photographing for 27 years now, 22 of which as a 
cinematographer. I'm quite surprised that a discussion of this sort has 
arisen among Leica M users. The Leica M, in my view, is a terrific tool 
for high-class snapshot or documentary photography, the kind of 
photography I like to practice in between jobs of a quite different and 
much more commercial kind.

For light measurement in documentary photography all you need is what the 
exposure meter of the M6 offers you (let's put automatic exposure apart): 
a reliable measurement of reflected light, with a preference for the 
center area of your field of view. Step down and shoot and don't think 
twice - or else the precise instant you were looking for has slipped away.

With a bit of practice and experience you can handle even more critical 
lighting situations such as low and high key subjects. You will know that 
you have to "overexpose" backlit scenes and snowscapes and to underexpose 
sunsets and people of dark complexion.

You must keep in mind that each and every exposure meter is dumb and 
programmed to "think", that what it is measuring is either a continuous 
surface of 50% reflection (medium grey) - a behaviour programmed onto 
exposure meters which measure reflected light (as the Leica M6's or 
spotmeters) - or, in the case of incident light measurement, to give the 
"right" exposure that will portray a medium grey as a medium grey, 
whatever is lighter as accordingly lighter, and whatever is darker as 
accordingly darker.

What you might loose by trusting incident light measurement is detail in 
the shaddows and/or detail in the lights, depending on the latitude that 
your film stock offers you and on the subject you are photographing. 
Remember, that as precise the exposure meter may be, it is dumb. You are 
called in to judge, in any case, what you see in front of you and what 
you want it to look like in the picture. If you are photographing a low 
key situation, for instance, you have to balance between two options: a 
reflected light measurement might result in a strong overexposure (which 
you might still be able to handle with comfort when printing, but not 
when shooting slides) while an incident light measurement could result in 
a relative underexposure, resulting in a loss of detail which you will 
never make up for.

Conclusion: Even the pros, who can't do without both types of 
measurement, will have to rely on their experience, in the end. With film 
stock getting more and more forgiving, the problems are getting more and 
more marginal, but if we are talking about non-documentary photography 
(or cinematography) you should better know where to put your lights and 
how to set and balance them before exposing.

When talking "documentary" photography, which I think Leica M talk is 
about, don't think twice, get a fresh battery and rely on that meter in 
there. "Underexpose" low key and "overexpose" high key situations, even 
give a "paleface" half a stop more, when you're real close...;-)

Hope that helps a bit, 
and have a nice holiday!

Lutz (Sling Guy) Konermann



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