P3D Re: back to topic: 1/30

[Tony Alderson <aifxtony@xxxxxxx>]

Well, hopefully we've all calmed down by now


> Tony Alderson wrote:
> 
> >yet in a later post you explain how the 1 in 30 rule does not apply
> >to stereo cameras with a fixed base (such as the Realist).

> Deering replied: 
> Huh?  Forgive me, but I never said this.  Never once.
> 

Yep, you're right. I misinterpreted another line you wrote. So
apparently you really don't understand "1 in 30", as it clearly does NOT
apply to stereo cameras with a fixed base. It may have been derived from
that situation, but it does not apply. Go look at Ferwerda, for example.
He discusses this "rule" in the context of cameras with a variable base.
So does Piper, so does every other stereo writer I can think of at the
moment. The Realist system does not prohibit close-ups. Why else do you
think the Realist company made close-up, medium and distant masks? As
you yourself point out, why do they focus up to a couple feet?

The 1 in 30 rule is about estimating an appropriate stereo base for a
given distance, not about how close one can get. You've set up a straw
man here, no wonder he's easy to knock down. You've made better
arguments than this.


> 
> What has been proven is that people can get too steamed to read what
> has been written.  All that stuff about *requiring* maximum stereo in
> each photo?  Never said that, either.
> 

Sorry if I've misinterpreted you, but it seemed to me this was implied
by your arguments. If you want a stereo of a subject from 4 ft to 4.5
ft, and you plug this in the depth-range equation as your near and far
distances with a deviation of 1.2mm, you'll get, in my opinion, an
absurdly large interaxial. Now, turning around your own phrase, if we
have to start making exceptions and qualifications for every case, then
MAOFD is not of much value, is it? ;-) Anyway, thanks for the
clarification of your position. Makes a lot more sense.

> Rather than post a list of things I have *not* said, I think I'll
> repeat my original point, which has remained the same:  The 1/30
> thing is no "rule", because it's wrong in a wide variety of
> situations. 

To some extent, you're complaining because you don't like the English
language. In this context, "rule" is short for "rule of thumb" which
means it's just a rough estimate. We don't mean a law of thermodynamics
here. Not even Themelis is dogmatic about this. In the last issue of
"Stereogram" he even criticized 1/30 himself as being of only limited
use, being merely a special case (with fixed variables) of the
depth-range equation. (He proposes another rule of thumb you probably
won't like either, however; 1/focal length.)

Speaking of getting too steamed to read the opposition, I think you have
missed Klooswyk's point. He is not defending 1 in 30 from nostalgia or
fossilization; he is arguing an angular analysis. As this is a more
generalized way of looking at stereo, and especially more to the point
in viewing stereos, I think you owe it to yourself to reread and
reconsider his statements. At least Abram is always well-mannered.
(Unlike me, for example...)

But yes Tom, when we are calm, we have more agreements than not. I've
only seen a few of your stereographs, but those are pretty good, so you
must have some grasp of the situation! In the future I'll try not to
read so much between the lines.

Yours in depth,

Tony Alderson

"The severest criticism is necessary for truth." - Charles Babbage