Archived posting to the Leica Users Group, 2001/02/07

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Subject: RE: [Leica] how can the 75 Lux focus go bad?
From: "Austin Franklin" <austin@darkroom.com>
Date: Wed, 7 Feb 2001 10:58:43 -0500

Yes, I did read your post, and I understand it, and believe it is
irrelevant.  Did you read my post?

> Okay Austin,
>
> I am speechless...
>
> So you think....
>
> You did actually read my post?
> e p
> ......oh well.
>
> Cheers,
>
> John
>
> > From: "austin@darkroom.com" <austin@darkroom.com>
> >
> > I disagree.  If you take the same lense, and use it on ANY
> size film, at the
> > same distance, you will get the same DOF.  Optics doesn't
> know what the film
> > size is, and adjust it self accordingly.  3' IS 3', no
> matter what the film
> > size is.
> >
> > I don't disagree that if you change the distance, to
> re-frame the image so it
> > is the same composition you will get different DOF, but
> that is not part of
> > the discussion...the DOF calculator keeps the same
> distance, just changes in
> > the film format change the resultant DOF it gives you.  I
> believe that is
> > wrong.
> >
> >> Depth of field is a factor of image size and relative
> aperture. The film
> >> format/ lens combination affects the image size. A 45mm
> lens in on a 4x5
> >> camera will record an object "smaller" in the final print
> than a 45mm on a
> >> 35mm camera. You could enlarge the 4x5 negative more than
> normally is done
> >> and print an identical image size (assuming you shot both
> cameras at the
> >> same subject distance) and achieve identical depth of
> field (and COC) but
> >> this is not normal practice.
> >
> >>>> http://www.silverlight.co.uk/resources/dof_calc.html
> >>>>
> >>>
> >>> This web page changes the DOF based on film format...why
> would film format
> >>> effect DOF?
> >
>