Re: Hyperfocal differences Realist vs. Revere 33

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

Steve Owsley writes:

>I pulled the Revere out and examined it and compared it to the Realist 
>camera.  The Revere 33 has much more generous tolerances for allowable 
>range of 'sharp' focus at a given f stop.

>Both of these cameras have 35 mm lenses.  Is it possible that the 
>design of the Revere lens allows for greater depth of field at a given 
>f-stop, or is it merely that the David White Company was more 
>conservative in their computations and recomendations?

The two companies probably used a different value for the "circle of
confusion" parameter to the DOF calculation.  The "circle of confusion"
is an amusing name for the size of a spot one is willing to call a point
(as opposed to a blur).

If one tolerates a larger circle of confusion, one can be "in-focus" over
a greater range of distances.  In truth, however, the image will be fuzzier
on the film than for a smaller COF.

The Realist manual states the size of the COF they used in their
calculations.  It would be interesting to compare them.  One should be
able to re-arrange the equation and solve for the COF value, given the
f-number, distances from the table, and focal length of the lens.

	-Greg


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