Doug Kerr
Well-known member
We have been fortunate here to receive many sophisticated discussions of exposure metering and the related issues.
Still, we often see such phrases as, "since the meter is calibrated to 18% reflectance . . .", and many variations on it. But not everybody knows what that even means, much less what it means to us.
I have published a number of articles that cover this issue from different vantage points, entangled with other concepts. Nevertheless, I have just completed a new article intended to just answer head-on the question, "what does that mean?".
The new article is entitled, Photographic Exposure Metering and the Infamous "18% Calibration", and is available here:
http://doug.kerr.home.att.net/pumpkin/index.htm#Exposure18
The article in particular includes a discussion of the significance of the mystical numbers "18%" and "12.8%".
It includes a brief discussion of gray card metering and a brief exploration of how a certain widely-followed calibration situation is in fact prescribed by one international standard and embraced by another.
It does not discuss at any length the implications of this calibration situation on the resulting image, on such matters as "how will a uniform-luminance scene be recorded", and the like, These issues are discussed in the various other articles with similar titles you will find in the index at The Pumpkin.
Still, we often see such phrases as, "since the meter is calibrated to 18% reflectance . . .", and many variations on it. But not everybody knows what that even means, much less what it means to us.
I have published a number of articles that cover this issue from different vantage points, entangled with other concepts. Nevertheless, I have just completed a new article intended to just answer head-on the question, "what does that mean?".
The new article is entitled, Photographic Exposure Metering and the Infamous "18% Calibration", and is available here:
http://doug.kerr.home.att.net/pumpkin/index.htm#Exposure18
The article in particular includes a discussion of the significance of the mystical numbers "18%" and "12.8%".
It includes a brief discussion of gray card metering and a brief exploration of how a certain widely-followed calibration situation is in fact prescribed by one international standard and embraced by another.
It does not discuss at any length the implications of this calibration situation on the resulting image, on such matters as "how will a uniform-luminance scene be recorded", and the like, These issues are discussed in the various other articles with similar titles you will find in the index at The Pumpkin.
