Reply to Re: MR4 meters

["C.M. Fortunko" <fortunko@boulder.nist.gov>]

Fred,

Thank you for the wonderful essay.

I went out to compare batteries and observed that my yardsticks were made of
rubber. OK. I learned a lesson.

I tend to believe now that the M6 light meter is not calibrated to 18%. That
is OK with me also. I just did not expect to find the variabilities between
the various meters. 

Now, after thinking about the experimental variables, I understand most of
the results. My main hope is that this understanding will not get in the way
of my photography.

Chris


At 12:52 PM 8/10/96 -0500, you wrote:
>This is my semi-annual message about a seemingly endless thread. 
>
>These are observations made as a photographer, not as a collector and
>not as a comparison shopper. In a paragraph or so I hope to share four
>decades of experience about a dozen or more light meters.
>
>1. On the grander scale of expensive and carefully made objects, light
>meters for photographers are relatively inexpensive items not made to
>great tolerances and not meant to be perfect. Smallness has usually been
>a main goal, and price of course. But great quality is not an issue with
>amateur products. Therefore, do not expect too much.
>
>Chris has observed what photographers have known for years, that same
>brand or competing brand light meters seldom reproduce the same readings
>reliably. Go into a camera store sometime and ask an idle salesperson to
>show you a dozen meters and take a reading of the same object with all
>of them. 
>
>And then there are the known difference among old CdS, Selenium, and all
>the new battery-operated meters. Each has its own unique response to
>color. They cannot all read the same.
>
>And there is the basic concept to deal with. We generally believe that
>all manufacturers use the 18% guideline and make their meters to deliver
>a reading based on an 18% target. That is just not true. Any
>manufacturer can use any formula it chooses. It can have one cell, 2, 4,
>5, 6, or 10 metering cells and read all over the frame, giving weight to
>one part or another (usually favoring the upper center for horizontals
>and screwing up thing on verticals). As the speaker at a computer
>conference one began his talk, <You want standards. You say there are no
>standards. Tell me what you will buy and I will make it a new standard.>
>
>Meters vary... when new, when old, when batteries are changed, when
>dropped or vibrated in airplanes, or just because entropy is a reality.
>
>2. That said, I find the main flaw in all this concern about accurate
>Leica meter readings rests in a fundamental fact. All Leica meters read
>reflected light... either from a window on top of your camera to a a
>behind-the-lens cell, to spots on the shutter curtain. It does not
>matter how well adjusted to 18% any meter is (and the 18% is no more and
>no less accurate than say 15% or 20% would be), if you are taking a
>reflected light meter reading of your subject, you will get an
>acceptable reading only part of the time.....the part that has a scene
>that just happens to be reflecting 18% back toward the camera. Want to
>know how often that is?  Most folks find it is about 80% of the time for
>family shots.
>
>That a reflected light meter works for anyone at all is a testimonial to
>film latitude (and the diligent work by a few dedicated photographers
>who really study a scene and try to find something that seems to be 18%
>reflective, or use of a gray card). The 5 stops or so latitude in color
>negative and b/w film saves the day for reflected light meters. Color
>slides are seldom right-on with such readings. (And I can already hear
>the incoming replies, <Oh, but mine are>.) They simply cannot be.
>
>Look at the place with the most invested in a day s photography. With
>movies costing tens of millions, every day is worth hundreds of
>thousands of dollars. You have never and will never see a film
>photographer, whose exposures have to be dead-on, use a reflected meter.
>He knows they do do not work. Only incident light is read when the
>readings are important. 
>
>Do some tests with slide film. Do a long and medium portrait of anyone
>against a white wall, then against a black wall, then in open shade, and
>then in the deep woods. Look at the reflected light results. Do the same
>with an incident light meter and look at the skin tones.
>
>Do portraits of a Caucasian, an Asian, an Indian, and a Black with a
>reflected light meter on slide film and see what you get. Of even
>cheaper, carry around an incident light meter for a while and see what
>it reads after your Leica meter gives you a reading. They both cannot be
>right, can they?
>
>I offer this conclusion. If you have and love the beautiful little Leica
>meters, by all means use them. But if you want truly accurate exposure
>readings for all films, use an incident light meter. But also remember,
>incident meters also vary because of the things mentioned in the first
>paragraph. Test a few to get one that seems to be reading accurately. 
>
>And now, to rest until winter........
>
>Fred Ward
>
>

****************************************************
C.M. Fortunko, Ph.D.
Group Leader, Materials Characterization (853.05)
National Institute of Standards and Technology
Materials Science and Engineering Laboratory
325 Broadway
Boulder, CO 80303

Voice phone:(303)497-3062      FAX:(303)497-5030
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