or what we mean for good stereoscopic product, a bad stereography and ill-effect.

BRIEF INTRODUCTION
For over half a century, the dominant market for stereoscopic productions has been to the United States of America for several reasons including the passion given to research of new technologies designed to emphasize the quality and excitement of movies to maintain consistently high levels of the audience flow and thus fuel the powerful industrial machine. To this end, went very well again to add scenes in which the stereoscopic instrument was supported by expected stereoscopic effects such as hands facing the audience, objects flying towards the viewer: this because it was immediately noticed that the public are very excited with this type of scene. On the other hand, if the stereoscopic effects were pushed behind the screen, the audience said that there were no 3D effects at all.

In this period of history emerged as a winning

technology IMAX that arrived in its development to produce a particular 70mm film and the presence of two parallel side by side lenses with an interocular distance of 64 mm, the average distance between a human's eyes: each lens feeds a separate roll of film.

The high quality of color and engraving that was obtained allowed a projection on large screens enough to cover virtually the entire visual field of the audience, thereby avoiding the problem of "conflict window" which will be discussed later. All this was supported by revolutionary high brightness lamps, so as to give full emphasis to the images on these huge screens. These screens also were often concave surface toward the viewer so as to give full correspondence between the reflected images and our physiological system for the interpretation of stereoscopic based on convergence on curved convergence plan based ("oroptero"). It was the heyday in which the traditional cinema allowed very long productions on 70mm film on large screens like "Cinemascope".
All this, however, had a great limitation in the high production costs so IMAX produced almost always documentaries of short duration, resulting in fast-moving parts of the audience every 30 minutes that justified these financial obligations.
Unfortunately, the need to lower production cost and the need to make movies with compatible TV screen, has been slowly abandoning this type of production, bringing the film closer to the format of 16:9 of digital cameras with the result that virtually all movie

theaters have abandoned super panoramic screens to make way for smaller screens with ratio 1:1,84 or at most with a ratio close to 1: 2.5.

TECHNICAL REMARKS
Using viewing windows more limited in size and ratio in

theaters and even more in a television screen, has brought a whole new series of delicate issues that you need to know and maintain a correct stereoscopic playback. We will try to summarize the key points that now require to use different technologies to achieve a good production.


The stereoscopic human system interpretation called "stereopsis," provides for the vision plan "collimated" (in which the image is recognized in the best way) of concave shape toward the viewer in relation to close objects and middle distance: all this, taping with parallel cameras as IMAX, and it was not possible because the two virtual images are printed on virtual flat levels, but in IMAX theaters thanks to projectors placed in an appropriate manner and with the screen-bowl, you

optimally reproduced this obligation. Today the best movie screens have small bending angles useful for the best reflection of light, but definitely not enough to reproduce the stereoscopic plane collimation.
From this follows that the first rule of stereoscopic shooting:
1 - with existing projection systems and flat-screen playback, is necessary, to 3D filming with optical positioned with angles of convergence acts to simulate a stereoscoipic curved plane collimation called "oroptero".

Parallel camera arrangement is absolutely unsuitable to the production of flat screens, because this technique forces the brain to a strong commitment to the interpretation of inconsistent pairs of images, the feeling of sickness that comes from watching movies shot with parallel optics, as much stronger as delicate and sensitive will be the viewer. Unfortunately, many stereoscopic productions of recent years use this old technology, probably, in our, opinion, for lack of knowledge of these physiological problems and the greatest ease of filming with parallel optics. You could say that for parallel shooting is not even required the presence of stereographers on the set, because during the shooting the two lenses will remain in a fixed position. All this also requires a demanding post-production work (in an attempt to bring the images to reproduce virtually the curved plane of collimation) with different functions of distortion present in the stereoscopic post production software: however, the result will never be a good quality effect, even remotely comparable to that achieved by converged techniques and also you will almost certainly reduce the final digital quality "printed" for zoom, distortion, etc., carried out in post production.

Another problem arising from the use of movie screens in which the viewer has the sense of clear-cut edge screen (as it falls within his field of vision), is the so-called "window conflict" or "stereo window violation" which, with parallel cameras, is often impossible to manage properly. A stereo window violation occurs when an object appears in front of the stereo window and is cut off by the window. It's a physical impossibility that a window frame, seemingly appearing behind the object, is able to obscure it. An actor or an object shot in the foreground or in the American plan they are "cut" from the edge of the screen below: in this situation, especially if the character is close to the camera, with the parallel technique we have a deviation, in negative parallax (diplopia crusade) for which our stereoscopic system of interpretation "automatically" will attempt to put the person out front to the audience ... But fortunately we are not stupid and the brain processes the following thinking "how can I see a human figure out of the screen if the lower part of the body appears behind the screen frame, as no visible ?"... All this represents a strong conflict for our brain that matures discomfort resulting from incoherent information. From this follows the second rule of stereoscopic shooting:
- It is necessary to intelligently manage those items cut from the edge of the screen, which is possible only with a good quality using the technique of converged shooting.

We have reported only two issues to manage stereoscopic shooting aimed at movie screens, there are many other rules that must be respected with the utmost attention, but we believe that these are already sufficient to give a definite feeling of inadequacy shooting with the parallel technique .

The "convergent" technique also allows you to have the simultaneous presence of parts of the scene even if partial extrusion from the screen (eg. An outstretched arm towards the viewer), while other components of the plan will be deep inside the screen (eg a far background): this combination will make the vision of the scene very realistic and impressive. The "parallel" technology instead, not allowing the reversal of convergence, will have all the components within the plane of the scene or screen or any screen outside of the plan (including any items cut from the edge screen with clear window-conflict) with a very strong feeling of nausea and muscular pain in the viewer's eyes (in some cases we have seen audience, who watched these bad works, declaring that they could not focus on objects: this is because the brain implements a particular form of defense by refusing to focus on images completely out of parallax).
This parallel technology exists in the majority of US movies that we can be defined as bad movies, because incoherent with our stereoscopic interpretation. We can call them completely bad even when they go to trigger a so intense struggle as to create profound disruption to sensitive people such as children who have a much closer interocular distances. A clear example of a "bad"product is when we have a divergence, which would mean that your eyes would angle outward. This is because the furthest point you could possible attempt to look at is at infinity and even infinity would only require that your eyes be angled perfectly parallel to each other. Our physiological system accepts the convergence or the maximum parallelism, but the divergence triggering, you can get to the phenomena of nausea, especially in extended projections.

The "convergent" technique also allows you to have the simultaneous presence of parts of the scene even if partial extrusion from the screen (eg. An outstretched arm towards the viewer), while other components of the plan will be deep inside the screen (eg a far background): this combination will make the vision of the scene very realistic and impressive. The "parallel" technology instead, not allowing the reversal of convergence, will have all the components within the plane of the scene or screen or any screen outside of the plan (including any items cut from the edge screen with clear window-conflict) with a very strong feeling of nausea and muscular pain in the viewer's eyes (in some cases we have seen audience, who watched these bad works, declaring that they could not focus on objects: this is because the brain implements a particular form of defense by refusing to focus on images completely out of parallax.

This parallel technology exists in the majority of US movies that we can be defined as bad movies, because incoherent with our stereoscopic interpretation. We can call them completely bad even when they go to trigger a so intense struggle as to create profound disruption to sensitive people such as children who have a much closer interocular distances. A clear example of a "bad"product is when we have a divergence, which would mean that your eyes would angle outward. This is because the furthest point you could possible attempt to look at is at infinity and even infinity would only require that your eyes be angled perfectly parallel to each other. Our physiological system accepts the convergence or the maximum parallelism, but the divergence triggering, you can get to the phenomena of nausea, especially in extended projections.

FINAL NOTE: The recovery technique implemented with variations on the angles and interocular distance convergence of the cameras, however, requires much more attention on the set for the endless permutations on the two variables involved to be calculated as a function of several parameters: the distances of the different planes ( by the actor in the foreground to the background), for addressing the problem of "conflict windows" and thus preventing the divergence of the optical axes of the viewer, etc.. Moreover, even using angles of convergence, you should be aware that you can implement very small corrections in post production. Necessarily, then you will have the assistance of a team of stereographic extended experience over the years, as it is necessary to have a good director of photography.
The results obtained are, however, far superior in quality and delight in the vision that will make even the two hours of a feature film compelling and free of discomfort.

Sala IMAX


Proiezione IMAX


Proiezione IMAX


Macchina da ripresa 3D IMAX


Sala cinematografica tradizionale