Re: LUG[Leica] Incident light measurement

[Henry Ambrose <digphoto@nashville.net>]

Eric Welch wrote:

>sometime around 12/23/99 4:56 AM, Frank Dernie at FrankDernie@compuserve.com
>was heard  to write:
>
>> 
>> ALL exposure meters are incident meters. Reflected light meters are simply
>> incident meters with optical and/or electronic compensation built in such
>> that when light reflected from an 18% grey subject is reflected back at
>> them they give a reading the same as a simple incident meter at the subject
>> would have given. thats all.
>
>Frank, you are flat wrong. I know physics just fine. Incident meter means
>the light falls on the sensor directly from the light source. That IS THE
>DEFINITION of incident meter. Reflective meter measures the light reflecting
>off the subject, not just 18% grey subjects, as you inaccurately describe.

I see it as two different ways of getting to the same point - desired 
exposure. I think that's what Frank was getting at.

The basic idea of exposure is that you have a visualization of the 
picture you want and then pick some part of it to be exposed a certain 
way.  The meter type is not relevant to the preceding sentence. (assuming 
that the meter is accurate and appropriate for the given scene)

Deciding "her skin is average" and adjusting for that with the incident 
reading is not that different from measuring with a spot meter and 
thinking "I'll place that area at zone VI" One starts with an assumption 
then a measurement. The other starts with a measurement followed by an 
assumption.
(go ahead - flame me, I'm ready)

Don't beleive it? Then go out and measure your gray card from varying 
angles with your spot meter.  Just small variations in angle will do. 
It'll read different. Every time. YOU still decide what to do with the 
information provided. 
>
>The camera measures the light and reports back how to make that tone 18%
>gray, it does not think that is 18 percent gray. It doesn't think at all! No
>one, but someone who doesn't know what they are talking about, thinks a Zone
>VIII tone is Zone V. 

Oh really? Why could you not place zone VIII scene on zone V exposure? - 
IF you chose to - IF you thought about it first! If maybe that was a 
route to the desired result. Why not?

In terms of  "thinking" about the desired end result I believe that the 
least amount of thinking occurs (and lots of bad exposures) with 
in-camera (reflective) meters and uninformed users. (Of course no one on 
this list falls into this category:) ) A huge example of reflective 
meters not helping. No meter is any good if you don't think!


>
>That's just the beginning. It also takes brains to interpret either kind of
>meter reading. Reflective metering allows for more accurate placement of
>tones, and if you can't see that, then there is no need to continue the
>discussion. Using an incident meter is more like using auto exposure, and
>reflective meters like manual. The latter gives more direct control over the
>results. 

Bull.  

The fact that someone is using a seperate meter is at least an indication 
that they are thinking about exposure.

Instead of saying reflective lets narrow it to spot reflective meters. 
Using a wider angle reflective meter is a sure way to NOT have a valid 
measurement for anything other than the average of what the meter sees 
reflected from the scene! Which oftentimes is just fine. This is the 
method of measurement for most pictures made in the world. Its dumbed 
down and works anyway because of a well evolved system of photography for 
the masses.

Place your incident on someone's caucasian cheek, read it and decide 
where you want their skin. You'll get essentially the same result as if 
you use a spot meter and then place the tone. Its just a matter of WHEN 
you make the decision about what subject in what zone. And yes, there are 
lots of times when one type of meter is more appropriate than another. 
And times when only one will really do.

Meters don't expose film - people do.
(great bumper sticker?)

>
>I know a lot of pro photographers who don't know squat about proper exposure
>and rely on the forgiving films they use to save their butts. 

Yeah right, like you never needed your butt saved. 

>For them the
>incident meter is ideal. Not that only bad and incompetent photographers use
>them, but in this case, it's the way to go.

How about maybe we stick to how-to-do-it-better instead of complaining 
about someone else doing it wrong?
>
>And on top of that, there is a wide range of quality of the photographs that
>are offered by pros. Just because a Pro uses an incident meter, or Minolta
>cameras, or Leicas and relective meters is secondary to their competence,
>and who they learned the trade from has a lot to do with how they work.

This part I can agree with.

> A pro is someone who makes more than 50 percent of their money via 
photography
>(IRS rule?) and that's about it. Anyone can call themselves pro. A lot of
>incompetence exists in the profession. At least as much as there is
>competence.
>
>--
>
>Eric Welch
>Carlsbad, CA
>http://www.neteze.com/ewelch
>
>Cynicism often masquerades for sophistication in our society, but more often
>than not it's merely an indicator of resentment.
> 
Best of exposures to all,

Henry Ambrose