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From: nishri@utcs.UUCP (Alex Nishri)
Newsgroups: net.rec.photo
Subject: Re: exposure stop formulae
Message-ID: <423@utcs.UUCP>
Date: Tue, 5-Feb-85 01:36:29 EST
Article-I.D.: utcs.423
Posted: Tue Feb  5 01:36:29 1985
Date-Received: Tue, 5-Feb-85 02:49:03 EST
References: <81@ISM780.UUCP>
Reply-To: nishri@utcs.UUCP (Alex Nishri)
Organization: University of Toronto - General Purpose UNIX
Lines: 21
Summary: 


Handy general equations to remember (known as APEX):

    EV = SV + BV = AV + TV


Where:

	EV = exposure value
	SV = LOG2 kS		(S arithmetic film speed; k constant)
	BV = LOG2 B/6		(B in foot-candles)
	AV = LOG2 f**2		(f-stop)
	TV = LOG2 (1/T)		(T exposure time in seconds)

The above equations are also sometimes presented as a simple SLAT table, where
SLAT stands for Speed + Light = Aperature + Time.

Alex Nishri
University of Toronto
UUCP: ... utcs!nishri
BITNET: alex at utoronto