P3D Re: 3D realism and focus cues

[roberts@xxxxxxxxxxxxxxxxx (John W Roberts)]

>From: michaelk@xxxxxxxxxxxxxxxxxx (Michael Kersenbrock)

>> >But if true, then the situation of everything being simultaneously in focus 
>> >is a "natural" and therefore acceptable thing for a stereo photograph
>> 
>> To make an analogy, I could say that most birds fly, and a bird is a kind of
>> animal, so a flying animal is a natural and acceptable thing...

>I think your analogy is silly and inappropriate.  

Since the silliness caused you to fail to see the appropriateness, let me
rephrase: you have made some good points in your posts, but the particular
statement to which I reacted contained a serious *logical error*, because it
makes an *unsupported assumption* (if the choice of assumptions is regarded
as part of the logical process). 

Your error was to assume that since a thing looks alright in a particular
context, the brain will most likely not be perceptive enough to detect
the inappropriateness in a different context. The bird analogy was one in
which the importance of context was obvious. The question of whether the
brain is capable of making use of subtle focus cues as a function of context
has yet to be resolved - but your use of the phrase "and therefore acceptable"
indicates that you *assume* context will not be an issue. I submit that this
is not something to be assumed, but something to be proven (or disproven).

>> >and therefore defocussing where one isn't looking shouldn't
>> >necessarily be an improvement, even for particular stereo photographs
>> >where one's eye would be defocussed in the not-looked at areas.

>	1. I didn't say it COULD not be an improvement, I just said
>           there is a reasonable argument saying that it MAY not be
>           significant 

Recall the context - Phil Palmer commented on January 15 that he had been
speculating on ways that computers might someday make stereo viewing more
lifelike. Eye tracking and real-time adjustment of focus was one possibility
mentioned. I don't know whether it would help or not, but I would encourage
him to think about it - that might lead to a breakthrough. Some of the
comments posted in response to Phil's post haven't been much more supportive
than "humph - might not work - better not try". (Yours wasn't that strong.)

Of course you can post whatever you want, but if it's something that might
tend to *discourage* a person from pursuing an idea, I hope you will be
extra careful to make sure that the line of reasoning is really valid.

>           and current all-in-focus technology be "acceptable".  
Of course. Thousands of people "accept" the current technology.
           
>	   One's eyes do not explode if everything is in focus 
>           simultaneously.  So I believe anyway.  In other words,
>           I suspected that the possible improvements not to be dramatic
>           due to the proposed viewer correction "correcting" something 
>           that in some situations, happens in real life.  In nature.

Again, the context issue. Lots of people like the current technology, but
also lots of people don't like it, get disoriented, get headaches, it doesn't
look real to them, and so on. That wouldn't happen if there weren't *some*
difference from real life. We can determine some of the differences, but
we haven't established which, if any, are key, or if the key differences are
things we haven't thought of yet. I support the increased use of 3D, which
requires that more people be able to use it, and that more people not have to
struggle to learn to view.

>> That doesn't mean we should all throw out our stereo cameras, but 
>I think it'd be throwing all of our viewers out.  We'd keep the camera.
Good point.

>> I don't think we should dismiss it as a possible area for future improvement.
>I agree with that, with emphasis on "possible".  
OK.

>It also *could* be that doing that... *might* make things worse...
>Particularly if there are any implementation side effects (such as 
>nonlinear response time requirements, etc).  

Excellent point. That was one of the issues I identified with Phil's
suggestion - response probably has to be *very* fast to be realistic. My
other concern (less crucial) is that convergence alone doesn't *always*
indicate the distance you're looking at. For example, you might be trying
to view a virtual image of a SIRDS. Scanning through the lens to help estimate
probable distance of focus might be feasible.

>I was *NOT* trying to make a naturist statement.  If the stereoscopic
>system were emulating "nature", for me, that'd mean that EVERYTHING
>would be fuzzy and out of focus...

By contemporary usage, I think maybe one of the definitions of "naturalist"
was what you had in mind. As far as I know (admittedly not too far), naturists
don't object to glasses. Or suntan lotion. :-)

You mentioned real-time adjustment of interocular. Larry Berlin has also
expressed interest in that. Maybe the two of you could cook up some ideas.

John R


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End of PHOTO-3D Digest 2526
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