Gray cards : the 12% - 18% controversy

Started Apr 13, 2013 | Questions thread
Shop cameras & lenses ▾
Senior MemberPosts: 5,233Gear list
Re: Gray cards : the 12% - 18% controversy
In reply to cquarksnow, Apr 14, 2013

cquarksnow wrote:

Given spot-metering with a Merrill based camera, what percentage would seem appropriate for a gray card ?



This is a transcript from one of the links by Doug Kerr that I posted earlier:

"Now, where can we get such a gray card of 12.8% reflectance? It isn’t easy. But we can easily acquire a gray card whose reflectance is 18%—all photo supply houses sell them. If we follow the scenario above with such a card as our “metering target”, the exposure recommended or set by the metering system will be 1/2 stop less than [that] needed to produce the effect we seek. (The greater illuminance seen from the 18% card will cause the metering system to feel that a lesser exposure is required than we [actually] need, by 1/2 stop). So, after we see the exposure that the metering system recommends (or actually sets) when the meter is regarding the 18% gray card, we [could] manually force the camera to use a 1/2 stop greater exposure and use that for the shot."

So, assuming the 'Merrill-based camera' to be compliant with the ISO standard, the answer to the actual question is . . .12.8%.

Having said all that, what's half a stop between friends?

-- hide signature --

SD9, SD10, EF-500, GH1.

 xpatUSA's gear list:xpatUSA's gear list
Sigma DP1s Sigma SD14 Sigma SD1 Merrill
selected answer This post was selected as the answer by the original poster.
Reply   Reply with quote   Complain
Post (hide subjects)Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow