Check the following DOF table you will know it is true. Try to input some
figures e.g a 85mm lens for 35mm system and 150mm for 6x6 system. They both
have more or less has the same angle of coverage, so that at the same
magnification the object distance is the same. You can see the DOF in 6x6
system is smaller and most important the 150mm lens's out-focus effect has
much sharper change, the background will be very soft even they are not far
away from the object (focus point).
That is why you need to stop down more for medium and larger format in order
to obtain the same DOF in 35mm.
http://members.home.net/gillettm/DOF.html
C.H.Ling
----- Original Message -----
From: "Mickey Trageser" <mickeytr@xxxxxxxxxxxxxxx>
> John,
> The 9mm is only superwide in respect to the 35mm format. The design of the
> lens in respect to the target frame should bring the depth of focus back
in
> perspective. If what you say is true, medium format wide angle lenses
would
> be unable to get the depth of focus equivilent to that on 35mm with
> equivilent coverage. True? I know we have some folks very knowledgable
about
> lens design. Perhaps they can expound on this?
> Mickey
>
> On Thursday 08 November 2001 09:25 am, you wrote:
> > Since the ccd is so small compared to film (The diagonal measurement of
the
> > 35mm frame being 48mm, normal lens is 50mm), the "normal" lens for your
> > average digital may be as short as 9mm. This is the equivalent of a
super
> > wide angle which has lots of depth of field. So even if you shoot wide
> > open, it is difficult to throw things in the background out of focus
> > because depth of field is still very deep.
> >
> > John Hermanson
> > ___________________________________
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