P3D Re: DOF Table on Realist lens cover varies among samples!

[Paul Talbot <ptww@xxxxxxxxx>]

Greg Wageman wrote:
> >> Perhaps they changed the size of the Circle of Confusion.  This is a key
> factor
> >> in DOF scales, and you're comparing apples to oranges unless you know this
> >> parameter.
> > (I queried):
> >Greg, do you mean "changed the parameter for purposes of the
> >calculations" or that the CoC of the lenses actually changed?
> The former...  [snip]

In which case aren't we down to semantics?  Observations by Mike K.
and me (jointly)--and Gabriel singlehandedly--were that the DOF tables
vary.  We want to know why.  A different CoC parameter would give
different DOF tables, but what does that tell about the cameras?
We're looking for why a different DOF table is specified, or, asking
the same question another way, why is a different CoC specified, as
the cameras and lenses (as far as we know) are identical?

> >I would hate to think of David White doing something down and dirty
> >like that!  ;)  It occurred to me to compare the DOF scales between
> >my retrofitted early Realist and my later Realist.  The dials are the
> >same!  
> I presume you're referring to the markings on the pointer plate; the markings on
> the focus knob only indicate the plane of focus and shouldn't change unless the
> focusing mechanism or lens design changed.

Forgive my shorthand; I was referring to the DOF ranges indicated
by looking at the dial and the markings on the plate together.

I'm not ready to accept the idea that this whole group is stumped
for the explanation of the DOF table/CoC difference.  Who's keeping
secrets out there?

Paul Talbot

P.S. As a matter of practicality, I suspect that a dial made for
the DOF scale on Mike K's Realist would have the same scale, but
would have different markings (for ease of use).  My dial has marks
at 3, 4, 5, 6, 8, 10, 15, 25, and Inf; a dial for his camera would
likely have somewhat different marks to make it easy to set focus
to the "Set to" value of the DOF table for his camera.


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