William Robb wrote:
----- Original Message ----- From: "Adam Maas"
Subject: Re: has anyone tried optibrite with a katzeye screen?
Many of the people over there still think that camera meters are
calibrated for 18% gray just because that's what Kodak gray cards are.
Funny you should mention that.
I've never been able to get a straight answer. I've heard 12%, 18%, and
a few other numbers.
What is the reflectivity standard for meter calibration?
It's supposed to be 12.7% according to the ANSI standard (ANSI
PH3.49-1971), but manufacturer's calibration varies somewhat from what
I've heard.
Couple of useful pages:
http://www.libraw.org/articles/zone-v-in-digital.html
http://www.richardhess.com/photo/18no.htm
The first reference I know of to the discrepancy between the 18% gray
card and actual reflectance standards was in the book "Post Exposure" by
Ctein.
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