Re: bellows extension

----- Original Message -----
From: "SteveS" <sgshiya@redshift.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, December 02, 2005 1:19 PM
Subject: Re: bellows extension

>
> ----- Original Message -----
> From: "Shannon Stoney" <sstoney@pdq.net>
> Subject: Re: bellows extension
>
>
> >
> > The 90mm lens I am using now (thanks, Clay!) is 3.5". So if it's racked
> > out to 7", that's two stops I guess. Somewhere in between would be about
5
> > 1/4", which would be one stop. I guess you could mark all these places
on
> > your camera.
> >
> > --shannon
>
> No. That would be one stop. One click on the diopter ring, actually . .
.
> the ratio is 4=one stop or two times the distance equals one click, which
is
> actually a half of a stop.
>
Don't know what you're trying to say here (what's a "diopter ring"?) but a
lens with an infinity backfocus distance of 3.5", when extended to 7" from
the film plane, will project an image that will cover 4x the area of the
image that is projected when focused at infinity. That requires a 2 stop
adjustment.

Wayne
Received on Fri Dec 2 15:50:09 2005