A couple of weeks ago there was some discussion here about
how the camera manufactures are calibrating their meter to
13% rather than 18%. Someone commented that Kodak is now
suggesting that you open up a 1/3 to 1/2 when using a gray
card to set exposure.
WHAT!!!!
18% gray was chosen because the real world approximates
that. If you average the exposure for all outdoor scenes it
comes out to 18% reflectivity. So if the meters are
calibrated to 13% you will always get the wrong exposure.
I do believe that maybe the meters really are calibrated to
13% that would explain why I get the best exposure when down
rating the exposure index of the film 1/3 to 1/2 stop. That
would compensate for the difference and give correctly
exposed film. An interesting aside is get the proper
response from my film scanner when I use ASA 320 instead of
400, or 80 instead of 100, with the films I use. Which
further leads me to suspect that the meters in my cameras
are off about 1/3 stop.
Does anyone have anything info to contradict the above?
BTW, 12.5% would indicate that he manufactures are using ND
filters to calibrate their meters from a reference standard
light source.
--Tom
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