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Re: [OM] external metering with extension tubes

Subject: Re: [OM] external metering with extension tubes
From: "Lama-Jim L'Hommedieu" <lamadoo@xxxxxxxx>
Date: Fri, 1 Aug 2003 14:50:17 -0400
Instead of calculating, here are 2 solutions and they both involve existing 
light:

1.  Auto exposure mode.
2.  Auto extension tubes in any mode you like.

How come I can't put extension tubes on the XA?  What a crime!

Lama, who's going on a road trip next week.  I'm taking every bit of shooting 
equipment I own.

----- Original Message ----- 
From: "Jeff Keller" <jrk_om@xxxxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Friday, August 01, 2003 1:39 AM
Subject: Re: [OM] external metering with extension tubes


> I believe the internal focusing changes the focal length. That would
> make it even more difficult to calculate.
> -jeff
> 
> ----- Original Message -----
> From: "Lama-Jim L'Hommedieu" <lamadoo@xxxxxxxx>
> >
> > I guess if you have internal focussing, like the AF camp usually does,
> LE is essentially zero?
> >
> > Lama
> >
> > From: "John A. Lind" If
> > > [the lens is] focused closer than [infinity], the lens is extended
> further by its internal
> > > helical, in addition to the extension tube, and that extension must
> be
> > > added as well.  The equation I use is similar, but also takes into
> account
> > > extension of the lens with its own focusing helical, FE:
> > >
> > > FF = (FL + LE + E)/FL
> >
> > FF = f-stop multiplier factor
> >
> > FL = focal length (nominal, when at infinity)
> >
> > E  = Extension tube length in same units as LE and the focal length
> >
> > LE = lens extension
> >
> >
> 
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