Archived posting to the Leica Users Group, 1999/01/12

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Subject: Re: [Leica] Electronic dependance
From: Eric Welch <ewelch@ponyexpress.net>
Date: Tue, 12 Jan 1999 09:27:12 -0600

> I use manual exposure for the most
>critical exposures and a 10% or 20% inaccurate shutter speed on a
>mechanical camera will give me a more accurate exposure than the 25% error
>which the electronic camera guarantees if the correct exposure is midway
>between the available half-stop increments. 

Where did you come to the conclusion that electronic shutters are
inaccurate, or only go in half-stop increments? First of all, your manual
shutter is twice as inaccurate by your reasoning. It only goes in whole
stop increments. Second, mechanical shutters are inherently less accurate,
or repeatable than electronic shutters. The difference is you know what
shutter speed you're using, and you have to tweak the aperture to get what
you want. Where with a mechanical camera, you are using a less accurate
shutter and tweaking both shutter speed and aperture. I'll take the more
accurate, repeatable shutter speeds. And the fact is, 1/10 stop seems to be
what the limit for discerning exposure differences is with chrome film.

You want differences that are accurate, then put the electronic shuttered
camera in auto exposure, and adjust your exposure with the AE lock or with
the exposure compensation. Then you've got an infinitely variable shutter
that is just as accurate as when it's set at definite stops. 

You set the shutter speed on 1/125 for example in an R8 and an M6. Which is
closer to 1/125? The R8. Why? Because electronic shutters are more
accurate. You want to increase the speed 1/2 stop. Set the R8 at 1/180.
Adjust the aperture up 1/2 stop, perfect representation of the EV up a half
stop. Try that with a mechanical shutter in the M6. Any way you slice it,
electronic shutters are more accurate, and since you're always adjusting
aperture against shutter speed, just as flexible in real terms, if not in
terms of using specific shutter speeds between 1/2 stops. Even then, you
can indirectly adjust that in AE.

Eric Welch
St. Joseph, MO
http://www.ponyexpress.net/~ewelch

What is the probability that something will happen according to the odds?