Originally Posted by
Mrportr8
"D) light meters are calibrated to expose for zone IV (not zone V like we all believed)"
I could not find the original article where I first read this. It was most likely tossed out with some other old magazines. But here's what I recall. The author set out to discover why there was such disparity among light meters, even the same model/manufacturer when that part of photography is so critical. I was reading on Alan Ross' blog that he had three meters and had eventually sent them all out for calibration so they would agree. As it turns out (at the time of the article) there was no standard for meter calibration. The manufacturers more or less each determined how they thought their systems would best function and adopted their own standards. By and large, most of them settled on a reflectance value for middle grey in the 10% - 12% range rather than 18%. The reasoning was that most average scenes included foliage and sky in an almost even split. The sky would wash out when shooting transparency film (negative film can handle a higher contrast scene and it can be printed to an acceptable value more easily) so by lowering the target exposure a more pleasing image would result. Read almost any meter instructions and they tell you grass or foliage is 18% reflectance, middle grey. This makes sense with meters in-camera and spot meters where lens flare is a component, but only for those "average" situations.
Now, if you do your own film tests with that meter and determine your personal film speed then this is irrelevant because the resultant film exposure index erases the error. In the end it does not matter if you rate Tri-X at 400, 320, 200 or 160 as long as you are getting good results and it is calibrated to your system (exposure, development, printing). If you skip film testing and calibrating YOUR SYSTEM then you are going to have a much harder time. I do not know if this carries over to incident meters as they are not affected by lens flare. Reflective meters without a lens system may also be different and were not covered by the article. I'll keep looking to find the original author but after a few days I doubt if my luck will improve.
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