Originally Posted by
Jerry Bodine
AA only used the SEI to get reflectance readings in terms of candles/meter^2, then mentally calculated the shutter/aperture settings from that as follows:
The shutter speed is the reciprocal of the c/ft^2, and the aperture is the square root of the film ASA (box rating). For example: if the reading is 200 c/ft^2 with ASA 64 film, then a shutter setting of 1/200 sec at f/8 would result in Zn V exposure. Then he'd adjust that for the preferred zone placement. That process came in handy for the "Moonrise" image when he couldn't find his meter in the rush to set up the camera, since he recalled (from experience) the c/ft^2 of the moon when at that position in the sky.
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