Because hyper focal does not only depend on focallength and aperature, but
also on the coc and this last depends on how critical the photografer is.
(Or de viewer in the end).

The second problem is that the focus distince is not calculated, but the
distance is set using a feedback system, bit similar to what we do when
focusing manually. We do not know the distance but try to make the
picture as sharp as we can. Most camera's don't have a clue what the
focusing distance is. Some camera's do have an approximate idea, which
can be used for flashing for example. But this is not precise enough to
set to a calculated focal distance.
Can a camera (or lens) be made to have exact focal distance info, yes,
but then the lens would be far more expensive, because now we focus
on the image and compensate in that process for some of the
tolerances of the lens. When calculating a setting, we do not compensate
for the tolerances of the lens.

ben

That would be OK is the first article itself could be relied on. However, that article's claims, like:
. A typical assumption for a full-frame digital camera or a 35mm film camera is that the photographer will make an 8"x10" inch print
that will be viewed at about 12"
. An 8"x10" print has a diameter of 325.28mm.
. A full sized sensor is 24mm x 36mm and has a diameter of 43.27mm
. Well, the human eye can resolve about four lines per mm (up close).
. That means that the human eye can barely see a circle with a diameter of about 0.25mm. Any circle with a diameter smaller than
that will appear as a point. ... So, a 0.25 mm circle on an 8"x10" print would barely be recognizable.
make the lot worse than useless - it's outright misleading. The facts are:

1. 8"x10" prints are NOT typical In the real world, they probably account for less than 0.1% of prints. Plus the accepted
industry standard for viewing distances is 14" - and that's for 6"x4", not the larger prints that most people view from farther
away. See Kodak's Tech Report E-58 on the Print Grain Index. Quote: "The PGI method specifies a common viewing distance
of 14 inches (36 cm) for all print sizes. The distance at which small (4 x 6-inch) prints are typically viewed is 14 inches. This is
also the approximate distance at which larger prints are usually inspected for graininess." Larger prints of course, are typically
viewed from even farther away than 6"x4" prints - not closer.

2. An 8"x10" print has a DIAGONAL of 325.28mm - not a diameter of 325.28mm. Its rectangular, not circular. Likewise, a full-sized
35mm film has a DIAGONAL of 43.27mm - not a diameter of 43.27mm, and you'd have to enlarge it to 8"x12" (ie 8.47 times, not the 7.5
times the article implies) before cropping an 8"x10" print from it.

3. As for the a 0.25mm circle, and the 4lines/mm claim, that translates to a measley 100dpi. Try printing any 8"x10" photo at 100dpi
and see if its good for anything other than throwing in the bin - certainly no good for viewing from 12"!! At that distance you need
at least 300dpi for a decent print.

Kind of makes a mockery of the article's nice neat maths.

That is a fair opinion, but that is not how people, in general, read
when looking up information on the web.  (There is a lot of research
on this, see for example, Jacob Nielsens books on Web usability).

When creating for a particular medium, I think the author need to
consider how a particular audience "reads" that medium.  In this
particular case, a brief comment with a hyperlink referring the
reader to part I for the definitions of CoC and DoF would have
been suffiscient.

As others has noted, there is some issues with part I as well.
However, I see no point in making further comments if Ron B. is not
reading the groups he posts in and is not interesting in suggestions
on how to improve his site.

I think everyone who takes issue with Ron's advice should email him
asking for a 100% refund of the price they paid him for it.