Exposure Guidelines Revisited

Posted in Artist's Journal by Jonathan on the May 31st, 2008

I’ve been experimenting with my recently acquired lens this week. Having a maximum aperture of f/5.6 I didn’t expect that the Schneider Super Symmar XL 150mm would be terribly much faster than my stalwart Ektar f/6.3. True, the new Schneider is only ^1/3 of a stop faster than the Ektar but today’s results belied that tiny fraction of a hole. Is a fraction of a hole still a hole? I smell a kōan in there somewhere.

My note’s from the exposure I tried today showed a sky at EV-15 ^2/3, and grass at EV-13^1/3 yet my exposure of one minute yielded overexposure. Curious. My instinct tells me that this has something to do with UV transmission. A cursory review of the technical data available from Schenider delivers a bewildering array of charts and graphs yet deeper examination yields some useful nuggets.

The transmittance diagram shows level response from ~480nm to ~640nm although to be fair, the transmittal range of the lens below 80% starts and ends at ~400nm and over 700nm respectively. My image today was predominantly battleship gray so color isn’t an issue but UV could be.

I’m still researching… more later.

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