Archived posting to the Leica Users Group, 2002/01/14

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Subject: Re: [Leica] Re: NEW M7 MAJOR CROCK-POT CROW PARMESAN
From: Rick Floyd <rick-floyd@mediaone.net>
Date: Mon, 14 Jan 2002 13:44:05 -0500

On 1/14/02 1:21 PM, "Rolfe Tessem" <rolfe@ldp.com> wrote:

> Let me clarify the comment on TTL flash. It is true that several
> manufacturers allow multiple units to be hooked up and triggered
> simultaneously, while having exposure controlled by the camera's TTL
> circuitry. The one I'm most familiar with is Quantum.
> 
> But all this buys you is the assurance that you will get a correct
> exposure on the film. The TTL stuff knows nothing about what kind of
> ratios you want between and among the various flash units. So how do you
> regulate the ratio? With all of them I'm familiar with, you have to
> physically position the units so the ratio will work out properly (one
> unit twice the distance from the subject as another, for example), since
> the TTL circuit is going to squelch all the units simultaneously once it
> senses that enough light has reached the film. If you're going to go to
> that kind of trouble, you may as well just use the units in manual,
> position them where you want, and meter the scene.
> 
> As far as I know, and I'm pretty sure about this, as I've described it
> above is how all the systems you mention work. Which is why I said that
> TTL flash metering is really only of utility when using a single unit.
> And I didn't say it was *just* for wedding photographers; I stated my
> opinion that it was probably designed with their needs in mind.

Rolfe:

You should have a look at the Canon E-TTL system.  Their system allows you
to have full wireless flash capabilities AND do ratioed A:B lighting up to
1:8 or 8:1 in 1/2 stop increments automatically.

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Replies: Reply from Rolfe Tessem <rolfe@ldp.com> (Re: [Leica] Re: NEW M7 MAJOR CROCK-POT CROW PARMESAN)