"Edouard Poor" <pov### [at] edouardinfo> wrote:

> I agree with Ricky - while the POV focal blur system has it's flaws, I think
> it gets the actual blur amount in front of and behind the focal plane correct.

The concept of 'hyperfocal distance' has been with me since I was a teenager,
when I used to shoot lots of B&W 35mm stills.  But I decided to look up the
actual definition(!) To my surprise, there are *two* definitions, both equally
valid (if slightly different as to the 'acceptable focus' range.) The first
assumes setting the camera focus at a point somewhere off in the distance
(though not at infinity) to get the maximum focus-range from 1/2 that distance
*to* infinity. The other assumes setting the camera focus *at* infinity, which
produces a nearly equal 'acceptable focus' range. (My own concept has always
been the former one.)

I looked at the actual equations for both 'hyperfocal distance' and the
'thin-lens approximation', and I'm still wondering if POV-Ray takes it all into
account. (I'm no optician, so I'm still trying to get the hang of how the two
equations are coupled together.) I guess I should just set up a POV test scene
looking at objects that proceed off into the distance, and just *see* if POV's
blur does mimic HD.

One thing I did come across was that hyperfocal distance is intimately tied to
the size of the film frame itself (or the size of the CCD sensor in a digital
camera), in relation to the lens diameter or focal length--or something like
that. For hyperfocal distance to have any meaning at all in the POV world, one
would have to assume that POV's rendered image size (say, 640 X 480 pixels)
*is* the film or sensor 'size'. I guess that's obvious, I don't know.

KW

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