Archived posting to the Leica Users Group, 1999/02/17

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Subject: Re: [Leica] Leica M5(metering)
From: Malcolm McCullough <blayne@mbox2.singnet.com.sg>
Date: Thu, 18 Feb 1999 00:58:59 +0800

>EV is strictly a function of shutter speed and aperture.   Just look at any
>Hasselblad C or CF lens to convince yourself.  Specifying exposure requires
>both EV and film speed.
>
>Dan C.
>


>>> The EV is a function
>>>of light AND film speed.
>>

Are we talking at cross-purposes here?
I understood Mark's original statement to mean that the required EV was
dependent on the intensity of light and the sensitivity of the film - that
is true, surely. However, EV itself is solely a function of speed and
aperture and is independent of film speed and the amount of light. These
are not contradictory statements. Any apparent contradiction is the fault
of my inability to explain myself!

I remember when I first used my father's Balda. You set the film speed on
the Gossen lightmeter and read off the EV (EV determined by film speed and
light). Then you set that EV on the lens and locked the shutter/aperture
relationship (EV being a description of shutter speed and aperture
relationship). Then you twisted both rings round to the combination you
required.
Regards,
Malcolm