Mailinglist Archives:
Infrared
Panorama
Photo-3D
Tech-3D
Sell-3D
MF3D
|
|
Notice |
This mailinglist archive is frozen since May 2001, i.e. it will stay online but will not be updated.
|
|
Rule-breaking
- From: P3D Gregory J. Wageman <gjw@xxxxxxxxxx>
- Subject: Rule-breaking
- Date: Tue, 24 Jun 1997 15:52:21 -0700
(Rather than reply individually to each post, I'm going to do so in
one rather lengthy one. Hopefully I won't elide so much as to
quote anyone out-of-context.)
I wrote:
>>Good point! If they converge, the window is at the plane where the
>>normals to the film planes intersect, but converging them introduces
>>keystone distortion and isn't recommended, so window@xxxxxxxx would
>>be the usual case, at least for educated stereographers. :-)
[Please note that I said "isn't recommended", not "forbidden", and
"usual case", not "only case".]
Paul Pascu replied:
>Does that mean that there's only one right way to take stereo pictures and
>if you do it any differently it's simply wrong?
This is a perfectly valid question, and one that I myself have asked of
every stereophotographic "rule". What I've learned, both here on this
list and through experimentation, is that there are at least two different
kinds of rules: rules that exist to make for comfortable viewing (or to
make viewing possible at all!), and "conventions". You may of course
break any rule you like, but if you break the former category, please
don't inflict the results on others. :-) Some examples of these types
of rules are:
o No vertical misalignment (causes eyestrain/headaches/unviewable images)
o No rotational errors (ditto)
o No excessive on-film horizontal deviation (ditto)
Similar rules which are somewhat more tolerant of being broken:
o No psuedo-stereos (wrong unless done deliberately for effect)
o No window violations (note, this is NOT the same as "breaking the window",
which IMO is a perfectly valid effect)
o Entire image must be in focus.
There are no "stereo police" who are going to break down your
door and confiscate your images which break the rules. But some rules
have a definite purpose (viewer comfort) and you risk public censure if
you ignore them and display your work to a knowlegable group.
>My question is, doesn't anyone ever do anything different ... break the
>"rules" and make it work for them? If so, what?
We recently had a discussion here about when it is OK to break the
"entire image in focus" rule. Several of us agree that it *can* be
succesfully broken, but not *always*. We've been unable, as yet, to
codify exactly *when*. When we can, I will adopt a "new" rule. There
still may be stereographers who will not agree, however, and it's good
to know that, too. I'm not afraid to be in the avant-guard, but I'm
not an anarchist either. :-)
Deliberate experimentation with psuedo-stereo was also discussed here.
Note the word "deliberate"; the images were not simply chosen at
random or simply because they were psuedo. Some artistic judgement was
exercised, even preplanning.
>But how can you have the [viewer feel like part of the scene] when
>this window is always seperating you from the image (except under certain
>situations)? With projection in particular, we can't get into the screen
>with the image but we can bring the image out to us.
The conventions regarding the stereo window came about because of the
practical necessity of having a border around an image, particularly
with 5-perf Realist and narrower formats. (Before anyone jumps on me
for claiming that the window rules were invented for Realist format,
that's not what I'm saying. It's just that the Realist image size and
shape in a Realist viewer makes the window a very significant part of
the viewing experience.)
I've already observed how the VR folks aim to immerse you by involving
your peripheral vision. I don't know of any panoramic, stereo cameras,
or viewers for that matter. But even with 8-perf, the image is only just
so tall, so there is a border that must be dealt with.
Given that, people learned from trial-and-error what looked "natural"
and what didn't. We've all stood inside a house and looked out a real
window, to see the scene lying beyond. The scene doesn't appear to jut
into the house. Given that observation, it is natural for a stereo image
to try to emulate this. I've also commented on how window violation
produces conflicting depth cues. This is another viewer-comfort issue
as well as a "realism" issue. As Dr. T. pointed out, only the sides
of the window usually have disparity (and hence 'depth'), so you can
"get away with" violating the bottom of the window easier than the top
or sides, if it isn't extreme. If you can find a "creative" way to
violate the window, by all means go ahead! But to me, every example
I've ever seen (or caused!) just looks "wrong" (as in "unnatural",
"strange" and even "disturbing in a bad way".)
Mike K. expressed a similar opinion:
> I think it's intended exactly the opposite way. It's the
>"educated stereographers" who do those "wrong" things (ideally). The "rules"
>are intended for beginners to follow to make it easier to obtain success
>and positive feedback on their initial attempts of stereo photography. Once
>past that stage, is the prudent willful breaking of the "rules" to gain
>intended effects.
To reiterate, you have to know *why* there are rules. Once you know
this, you can decide intelligently if and when to break them. You have
to realize that stereography has over a 100-year history. Some quite
clever people have been thinking about these things for a long time.
It would be somewhat arrogant of me to think that I could out-think
all of them. Still, sensibilities change, and where the only reason
for a rule is convention, this can be changed. :-)
Gabriel Jacob wrote:
>This is all very true as Mike K. mentions but Paul, I think Greg W.
>comments are valid for NOT converging cameras. This would be one of
>the last intentions of a stereophotographer and wouldn't normally be
>for any desired effect.
Paul responded:
>Maybe none that you'd want. Does that then make it an absolute "wrong?" As
>Dr.T points out and as you note below, there are reasons that someone might
>want to converge cameras. The "desired effect" that you are speaking of
>would seem to be the effect of duplicating reality. That was the point of
>my post - why limited images to that?
Dr. T. already pointed out some situations in which some toe-in is
necessary, or even required. But the examples he cited all used a
very small amount. In an extreme case, the perspective distortion
would be such that the images wouldn't fuse properly, because the
right side of the right image would be so much larger than its
corresponding point on the right side of the left image. Again,
while avoiding distortions of reality may be a part of the reason,
there is also a practical reason: too much, and it doesn't work!
Also, in virtually every example there are ways to avoid needing any
toe-in, most requiring more flexibility in mounting (custom masking,
etc.). In his own words:
>What's my point? Don't let unwanted deviations stop you from recording or
>viewing a stereo pair if that's the only way to do it. But, obviously, in
>most cases of twin or single camera stereo photography, that's not the only
>way to do it.
Mike K. added:
>If one were to ask "is there any rule that can't be broken with acceptable
>results by someone very skilled in stereo photography". The answer would
>be yes, but for rules like "don't leave the lens cap on for the whole roll"
>or "put film in the camera". There also are "really-gross-result"
>rules that only would be acceptable on "modern art" terms, but for the most
>part -- even for making things keystone on purpose -- I believe that most
>participants think that rules can be broken by someone very skilled and/or
>lucky.
You can break the view-comfort rules to your heart's content. Just don't
show the result to me, I value my eyesight and dislike headaches. :-)
The rest are fair game for experimentation, IMO.
Kenneth Luker wrote:
>The distilled wisdom of what is done and what is not done in stereo
>photography has grown to what it is through scores of years of trial
>and error, criticism and daring. If one wants to do stereo
>photography that is accepted as mainstream and "correct," it can be
>done by "following the rules." Anything else will probably trigger
>criticism from the old guard. Anything else will possibly be labeled
>as "bad."
I wouldn't go so far. Many people are creatively breaking many of
the "rules", as detailed above. But they know which rules they can
break, and they are using artistic judgement in evaluating their
results. They're not just "puking onto a canvas" and calling it a
Jackson Pollock. :-)
>When Brahms ruled music, the rules of good music were similarly well
>known, so when Mahler experimented with new sonorities, they sounded
>brash and unacceptable. That was nothing compared with the total
>dissonance and lack of tonality of Schoenberg and Webern, which broke
>every rule in the book. To Brahms, the new music was never
>acceptable, but many people now love Mahler.
There is truth in this analogy; however, no matter what dissonances
one uses in composition, one can't damage the listener's ears, only
offend their artistic sensibilities. Unfortunately due to the nature of
vision, a badly-mounted stereo *can* cause physical pain in the viewer.
Whew! Thus endeth the lesson. I hope it was useful. :-)
-Greg W.
------------------------------
End of PHOTO-3D Digest 2148
***************************
***************************
Trouble? Send e-mail to
wier@xxxxxxxxxxxxxxx
To unsubscribe select one of the following,
place it in the BODY of a message and send it to:
listserv@xxxxxxxxxxxxxxx
unsubscribe photo-3d
unsubscribe sell-3d
unsubscribe mc68hc11
unsubscribe overland-trails
unsubscribe icom
***************************
|