Patent Publication Number: US-2011063727-A1

Title: Method and system with indicating marks for projection film

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present patent application claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 61/243,099, “Method and System with Indicating Marks for Three-Dimensional (3D) Projection Film,” filed on Sep. 16, 2009. The teachings of the above-identified provisional patent application are expressly incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to projection film and, more particularly, to the use of indicating marks on the projection film for delineating gap regions between images that are either more appropriate or less appropriate for cutting and splicing. 
     BACKGROUND OF THE INVENTION 
     The current wave of three-dimensional (3D) films is gaining popularity, which is made possible by the ease of use of digital technology and especially 3D digital cinema projection systems. However, the availability of new 3D digital cinema projection systems has been inadequate to keep pace with demand the demand for the new systems. Moreover, theater owners are finding that the changeover to the 3D digital cinema projection systems is very expensive business proposition. As a result, there is currently a move to satisfy the demand for 3D films without the use of digital technology by deploying stereoscopic film prints for presentation using a stereoscopic 3D projector. 
     Stereoscopic film prints are subject to all the same damages problems of any non-digital film media, especially breakage, tearing, and burning of the film itself. Experience from earlier 3D film systems cautions that, when a film is damaged and is therefore in need of repair by splicing, there is a substantial chance that the splicing and/or editing will be made incorrectly. For example, the splice can be incorrect when a segment of film cut on an inter-frame line is mated directly to a segment of film cut on an intra-frame line. From a viewing audience perspective, the effect of such an incorrect splice is severe eye strain, which can be an unpleasant and uncomfortable experience. 
     3D films have been produced with both thick and thin separation lines between images wherein the thick separation line is placed between left and right partial images in the same stereoscopic image pair, in which the thin separation line is placed at a position between adjacent frames parallel to the thick separation line (e.g., see ISCO OPTIC Instruction Manual for Stereovision-3D, from ISCO-OPTIC GmbH, Göttingen, Germany). These separation lines were apparently used to assist in film centering in the film gate as well as in splicing operations. However, the appearance of these parallel lines is not sufficiently different to prevent the occurrence of splicing errors. Furthermore, the subsequent detection of a splicing error and confirmation of the validity of the splice in a film using these separation lines would be difficult, if not impossible, to locate easily visually. This difficulty arises because the combination of these two separation lines in a film splice appears to be substantially identical to either one of these lines, for most any cut location. 
     Other problems can arise when the position for making a splice is incorrectly identified or when the splice is incorrectly made. For example, during proper operation of the system, the right-eye image and the left-eye image of a stereoscopic pair provided in a film are projected through a dual lens single-projector 3D film system so that the two images of the pair are substantially superimposed on the viewing screen. Care must be taken during film editing for the stereoscopic film to avoid any disruption in the proper sequencing and alternation of right- and left-eye images. 
     Needless to say, the known prior methods and apparatus appear to lack any suitable solutions for overcoming the problems related to both identifying clearly and accurately the position at which a film should be cut for splicing and confirming the validity of the splice after the splice has been made. 
     SUMMARY OF THE INVENTION 
     Splices can be made and validated accurately at a clearly identified position in a film in accordance with the principles of the present invention by introducing first and second indicia onto the film to indicate a location where cuts and splices can and cannot be made, respectively. The first and second indicia are sufficiently different from each other that, when combined by virtue of an incorrect cut and splice, they form a third indicia that is different again from each of the first and second indicia. 
     Indicia are established on the film to clearly indicate locations where cuts for splices may and may not be safely and correctly made. These indicia are different from each other to signify whether a cut can or cannot be made in the vicinity of the respective indicia. Differences can be exhibited in terms of one or more of a distinctive shape or size or orientation or pattern of the indicia. When cuts and splices are correctly performed, the resulting indicia in the vicinity of the splice match substantially one of the two original indicia. When cuts and splices are incorrectly executed, the resulting indicia in the vicinity of the faulty cut and splice will be third indicia, each third indicia being a combination of portions of the two original indicia. Third indicia will be different from each of the two original indicia and will therefore be readily apparent to be indicative of the presence of an incorrect cut and splice. 
     One aspect of the invention provides a film, which includes a plurality of images arranged in sequential order, each of a plurality of gaps separating two adjacent images of the plurality of images, a first indicating mark for identifying a region for disallowing cutting of the film, and a second indicating mark for identifying a region proximate one of the gaps for allowing cutting of the film. The second indicating mark exhibits discernibly different properties from the first indicating mark, and any combination of cut portions of each of the first and second indicating marks results in a third indicating mark that is discernibly different from the first and second indicating marks. 
     Another aspect of the invention provides a film that includes a plurality of stereoscopic image pairs of first and second images arranged in sequential order, a first indicating mark for identifying a region for disallowing cutting of the film positioned substantially alongside an intra-frame gap formed between first and second adjacent images from a same stereoscopic image pair, and a second indicating mark for identifying a region for allowing cutting of the film positioned substantially alongside an inter-frame gap formed between first and second adjacent images from different stereoscopic image pairs. The second indicating mark exhibits discernibly different properties from the first indicating mark, and any combination of cut portions of each of the first and second indicating marks results in a third indicating mark which is discernibly different from the first and second indicating marks. 
     Yet another aspect of the invention provides a method for producing a film, which includes a plurality of pairs of first and second images arranged in sequential order, with an inter-frame gap formed between first and second adjacent images from different consecutive pairs of stereoscopic images, and an intra-frame gap formed between first and second adjacent images from a same pair of stereoscopic images. The method includes writing a first indicating mark to the film in proximity to the intra-frame gap with a film recorder, the first indicating mark for identifying a region for disallowing cutting of the film positioned substantially alongside the intra-frame gap, and writing a second indicating mark to the film in proximity to the inter-frame gap with a film recorder, the second indicating mark for identifying a region for allowing cutting of the film positioned substantially alongside the inter-frame gap. The second indicating mark exhibits discernibly different properties from the first indicating mark, and any combination of cut portions of each of the first and second indicating marks results in a third indicating mark which is discernibly different from the first and second indicating marks. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Even if described in one particular manner, it should be clear that implementations may be configured or embodied in various manners. For example, an implementation may be performed as a method, or embodied as an apparatus configured to perform a set of operations, or embodied as an apparatus storing instructions for performing a set of operations. Other aspects and features will become apparent from the following detailed description considered in conjunction with the accompanying drawings and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  illustrates some elements of a film projector with a dual lens system and polarizers for showing stereoscopic film; 
         FIG. 2  is stereoscopic film including the indicia or indicating marks in accordance with the principles of the present invention; 
         FIG. 3  is a stereoscopic film including the indicia or indicating marks in accordance with the principles of the present invention wherein the film is shown to have an incorrect splice; and 
         FIG. 4  illustrates another embodiment of a film including indicating marks in accordance with the principles of the present invention. 
     
    
    
     The exemplary embodiments set out herein illustrate preferred embodiments of the invention, and such exemplary embodiments are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION 
     The description herein is generally presented in terms of stereoscopic film and stereoscopic image pairs for 3D presentations. But it will be understood that the principles of the present invention are also applicable to 2D films and images, as will be explained in more detail below. 
     In accordance with the principles of the present invention, indicia are established on the film to clearly indicate locations where cuts for splices may and may not be safely or correctly made. These indicia are different from each other to signify whether a cut can or cannot be properly made in the vicinity of the respective indicia. Differences can be exhibited in terms of one or more of a distinctive shape or size or orientation or pattern of the indicia. When cuts and splices are correctly performed, the resulting indicia in the vicinity of the splice match substantially one of the two original indicia. When cuts and splices are incorrectly executed, the resulting indicia in the vicinity of the faulty cut and splice will be a third indicia that is a combination of portions of the two original indicia. This third indicia will be different from each of the two original indicia and will therefore be readily apparent to be indicative of the presence of an incorrect cut and splice. 
       FIG. 1  shows an over-under lens 3D film projection system  100 , also called a dual-lens 3D film projection system or projector. Rectangular left-eye image  122  and rectangular right-eye image  123 , both on 3D film  120 , are simultaneously illuminated by a light source and condenser optics, collectively called illuminator  107 , which is located behind the film while framed by aperture plate  110  such that all other images on film  120  are not visible because these images are covered or otherwise obscured by the opaque portion of the aperture plate. It will be apparent to persons skilled in this art that only the inner edge of the aperture is illustrated in this figure for clarity purposes. The left- and right-eye images, which together form a stereoscopic image pair and are visible through aperture plate  110 , are projected by over-under lens system  130  onto screen  150  where the images are generally aligned and superimposed on each other such that the tops of both projected images are aligned at the top edge  152  of the screen viewing area, and the bottoms of the projected images are aligned at the bottom edge  153  of the screen viewing area. 
     Film projector  100 , which is depicted not to scale, includes an illuminator  107  in this embodiment that includes a high intensity lamp such as arc lamp  101  having envelope  102  at the center of which is a luminous arc. Reflector  103  is shown in this exemplary embodiment as substantially elliptically shaped to follow an ellipse  106  for reflecting light rays  104  from the luminous arc near the first focal point of ellipse  106  to form an image  105  of the arc near the second focal point of ellipse  106 . For most film projectors, image  105  of the luminous arc is formed at or near the film gate, which is shown here as aperture  110  cut into an aperture plate. Aperture  110  is depicted in  FIG. 1  as an opening for which only the boundary of the opening in the aperture plate is shown. In this way, the illumination from the luminous arc is provided as a smooth field, providing adequate illumination over the entirety of the opening for aperture  110 . 
     Stereoscopic film  120  comprises film substrate  121  having a row of perforations  125  along each edge. The perforations allow for engagement by a sprocket or other such mechanism (none shown) to advance the film smoothly and continuously from one image to the next. As mentioned above, the images on film  120  are grouped in pairs of left and right images. Stereoscopic image pairs (R 1 , L 1 ), (R 2 , L 2 ), and (R 3 , L 3 ) as shown in  FIG. 1  are adjacent image pairs provided along film  120 . For example, the stereoscopic image pair including images R 2  and L 2  corresponds to a right-eye image  122  and left-eye image  123 , respectively. Both images from a stereoscopic image pair are simultaneously illuminated while within the opening formed by aperture  110 . Images in the same stereoscopic pair such as images  122  (R 2 ) and  123  (L 2 ) are separated from each other by a gap defined as intra-frame gap  124 . Consecutive stereoscopic image pairs, or two adjacent images (e.g., left- and right-eye images) belonging to different stereoscopic image pairs, are separated from each other by a gap defined as inter-frame gap  128 . Inter-frame gap  128  may or may not exhibit the same dimensions as intra-frame gap  124 . Due to the inverting nature of the projector system  100 , the images on the film are provided in the projector in an inverted manner such that each image will be shown in its upright orientation when projected on the screen. 
     Lens system  130  comprises lens body  131  having an entrance end  133  and an exit end  134 . Entrance end  133  faces film  120  and exit end  134  faces screen  150 . In this embodiment, lens system  130  is a stereoscopic dual lens having an upper portion for projecting right-eye images and a lower portion for projecting left-eye images. The upper portion of lens system  130  includes entrance lens element  136  on the film side and exit lens element  138  on the screen side. The lower portion of the lens system includes entrance lens element  137  on the film side and exit lens element  139  on the screen side. Upper and lower portions of lens system  130  are separated by gap  132 . Gap  132  is controllably adjustable by adjustment element  135  to have a variable gap width that can be expanded or contracted. In this embodiment, gap  132  is lined with a coating or the like to prevent leakage of light between the upper and lower portions of the lens system. 
     Lens system  130  also includes a filter module or assembly  140 . Filter assembly  140  can include one or more of any of linear or circular polarizers or other non-polarizing filter elements, such as red/blue filters for anaglyphic 3D or multi-band interference filters, all of which are well known in the art and are suitable for separating the right- and left-eye images so that an audience member  160  can perceive a stereoscopic presentation. 
     In  FIG. 1 , a right-eye linear polarizer  142  is shown having a vertically oriented polarization axis  144 , and a left-eye linear polarizer  143  is shown having a horizontally oriented polarization axis  145 . Light emitted from the illuminator  107  passes through right-eye image  122  as a collection of light rays represented by centerline  126 , which is imaged on screen  150  by the upper portion of lens system  130 . The portion of light rays transmitted by polarizer  142 , which is represented by centerline  146 , and incident on screen  150  is polarized substantially parallel to polarization axis  144 . In a similar manner, light emitted from the illuminator  107  passes through left-eye image  123  as a collection of light rays represented by centerline  127 , which is imaged on screen  150  by the lower portion of lens system  130 . The portion of light rays transmitted by polarizer  143 , which is represented by centerline  147 , and incident on screen  150  is polarized substantially parallel to polarization axis  145 . 
     When properly aligned, the projections of right-eye image  122  and left-eye image  123  are substantially superimposed on screen  150 . Both projected images have their respective centers substantially co-located at screen center  151 , as represented in  FIG. 1  by the convergence of centerlines  146  and  147 . Upon projection, the tops of images  122  and  123  are both imaged substantially along top  152  of screen  150 , and the bottom of images  122  and  123  are both projected substantially along bottom  153  of screen  150 . 
     When filter module  140  employs polarizing components, such as linear polarizers  142  and  143 , screen  150  should exhibit a polarization preserving property. One such polarization preserving screen is a silver screen. On the other hand, when filter module  140  does not employ polarizing component, screen  150  may be realized without the need for a polarization preserving property. 
     Audience member  160  is provided with 3D glasses with a right-eye portion  171  and a left-eye portion  181 . Since polarization elements are used in the lens system, the 3D glasses include right-eye portion  171  comprising a linear polarizer  172  having an axis of polarization  173  in a first direction, and left-eye portion  181  comprising a linear polarizer  182  having an axis of polarization  183  in a second direction that is orthogonal to the first direction for polarization axis  173 . In other embodiments where circularly polarization elements are employed in the lens system—such as where clockwise and counter-clockwise circular polarizations are used—for projecting the respective stereoscopic images, 3D glasses will be provided with corresponding circular polarizers in the two eye portions. 
     As shown in the exemplary embodiment of  FIG. 1 , when audience member  160  is seated and facing screen  150 , polarization axis  173  is oriented substantially parallel to polarization axis  144  such that the projected right-eye images after reflection from screen  150  pass through right-eye polarizer  172  for viewing by audience member  160 . The same reflected light for the projected right-eye images will not pass through left-eye polarizer  182 , since polarization axis  144  of the right-eye images is substantially perpendicular to axis  183  in left-eye polarizer  182 . Thus, only the projection of right-eye image  122  reaches the right-eye  170  of audience member  160 . In a similar manner, only the projection of left-eye image  123  reaches the left-eye  180  of audience member  160  because polarization axis  145  of the left-eye images is substantially perpendicular to axis  173  in right-eye polarizer  172 . 
     In the description herein, various terms may be used to explain the marks placed on the film in accordance with the principles of the present invention. These terms may include “marks”, “indicia”, “tick marks”, “warning bars”, “indicating marks”, “indicator marks”, and the like. The use of any or all of these terms in intended to convey the same meaning without limitation or modification, unless expressly stated to the contrary. 
       FIG. 2  shows a film print  120  including marks  207  and  208  in accordance with the principles of the present invention to identify locations where a cut for an edit may occur, and locations where a cut should not be made, respectively. The use of these marks permits easy identification of both a splice that represents a correct film edit preserving the alternating right-eye image, left-eye image sequence, and a splice that represents an incorrect film edit that results in a pseudoscopic image sequence, which disrupts and reverses the alternating right-eye image, left-eye image sequence (such that the order in which the right-eye image and the left-eye image appears in the sequence is reversed, and the images seen by the left- and right-eyes are out of synchronization by about 1/24 second). 
     Film print  120  has a number of stereoscopic image pairs arranged in an uninterrupted sequence of alternating right- and left-images. Right- and left-eye images  122  and  123 , respectively, of the same stereoscopic pair (R 2 , L 2 ) are representative images in the film reel. Right-eye image  122  and left-eye image  123  are each bounded by a respective frame boundary, shown as a maximum extent of rectangular area  205 . Rectangular area  205 , in turn, defines a maximum extent for a corresponding projected image. In one example, the rectangle  205  corresponds to the maximum extent of an image having a standard width (W) of 0.825″ on the film, based on a well known film format. It should be appreciated that rectangular areas  205  are not generally present or actually visible on the film. Instead, each rectangle can be considered as a virtual geometric entity to assist in the definition and understanding of image and non-image areas on the film. The size of the rectangular area is usually set by standard or convention. Regions inside the boundaries of rectangular area  205  are considered as image areas, and generally contain image content. Portions of the regions within rectangular area  205  are shown in black for ease of comprehension. 
     Actual dimensions for the rectangular areas  205  are typically determined in accordance with the format selected for the stereoscopic presentation. In the exemplary embodiment shown in  FIG. 2 , the dimensions for a standard 35 mm film run a four-perforation inter-frame height of 0.748 inches (e.g., the inter-frame height corresponds to the distance between two indicia  207  that will be discussed below). The height of a stereoscopic image can be determined as half of the inter-frame height less half the sum of the intra-frame gap  124  and inter-frame gap  128 . With a 0.825″ maximum image width and an aspect ratio of 2.39:1 (scope) for each image, the image height will be about 0.345″. For a symmetric frame gap configuration, in which the inter-frame gap  128  equals the intra-frame gap  124 , the gap distance will be approximately 0.029″. Clearly, these gap dimensions will be different for an asymmetric gap configuration. In other embodiments that are based on different film formats or standards, different dimensions may apply. It should be understood that the principles of the present invention apply equally to all known film formats or standards and to both asymmetric and symmetric gap configurations. 
     Outer edges  206  outside the rectangular areas  205  represent the expected extent of the camera aperture. That is, outer edges  206  delineate that portion of film print  120  corresponding to the portion of a film negative that would be exposed by a camera or a film recorder. Ancillary information may be introduced onto the film beyond outer edges  206 . For example, as shown in  FIG. 2 , analog optical sound tracks  201  are shown on the film beyond edges  206 . Similarly, digital optical sound tracks, such as inter-perforation sound track  201 ′ and extra-perforation digital sound track  201 ″, are also shown on the film beyond edges  206 . Perforations  125  are also formed on the film in the region beyond outer edges  206 . Outer edges  206  are not generally marked on the film but are virtual geometric entities which are governed in practice by standards and industry conventions. 
       FIG. 2  shows indicating marks  207  and  208  in different regions of the film. Indicator mark  207  is positioned in the vicinity of inter-frame gap  128 , whereas indicator mark  208  is positioned in the vicinity of intra-frame gap  124 . These indicating marks or indicia are further positioned outside the image regions in the areas between outer edge  206  and the frame boundary for rectangular area  205 . The region in which the indicating marks are placed generally appears black or dark as shown in  FIG. 2 . Contrast between the indicating marks and the background color of the region in which they are positioned can greatly facilitate performance and accuracy of operations such as film cutting, splicing, and film inspection, as further discussed below. In one exemplary embodiment, indicating marks  207  and  208  appear as blank or bright marks against a dark background. 
     Stereoscopic film can be confusing for an individual tasked with editing the film print. In general, it is not apparent where a pair of images begins and ends or even which two consecutive or adjacent images belong to the same pair. As seen in  FIG. 1  and  FIG. 2 , the right- and left-eye images of a stereoscopic pair are separated by intra-frame gap  124 . Intra-frame gap  124  appears to be rather similar to inter-frame gap  128 , which occurs between consecutive stereoscopic pairs, i.e., between two adjacent left- and right-images that belong to two different stereoscopic image pairs. Without any signs to guide an editor concerning the appearance of inter-frame gaps and intra-frame gaps, errors can easily occur during editing or repair of a stereoscopic film. For example, when a stereoscopic film  120  is cut at an intra-frame gap  124  and then spliced to another strip of stereoscopic film cut at inter-frame gap  128 , the two adjacent or consecutive images (on either side of this splice) would be both right-eye images or both left-eye images. 
     Furthermore, the portion of the edited film following the splice will produce a sequence of images in which the order of the left- and right-eye images will be reversed or interchanged compared to the intended (or correct) order. That is, the projected right-eye image will be seen by the left eye, and the projected left-eye image will be seen by the right eye. In industry parlance, the projected presentation will switch from being stereoscopic to being pseudoscopic. Compounding this undesirable experience, of the right- and left-eye images projected simultaneously and at a frame rate of 24 frames/second, the right-eye image represents the scene at a time 1/24 second earlier than the left-eye image (since the right-eye image belongs to a stereoscopic pair X and the left-eye image belongs to the next stereoscopic pair X+1). The presence of indicating marks  207  and  208  on the film print help to avoid and minimize the occurrence of such errors during editing. Moreover, the presence of indicating marks  207  and  208  aid in the detection of such an error in the film subsequent to editing. 
     It is important to avoid separating a stereoscopic pair of images by cutting so that a stereoscopic image pair would be kept together during editing. By avoid this cutting error, it is less likely that images associated with the same eye would be spliced together to form adjacent images as an incorrect stereoscopic pair. 
     In accordance with the principles of the present invention, the film print  120  is provided with at least a first type of indicating mark, such as mark  208 , to indicate or identify locations at which a cut should not be made. As shown in  FIG. 2 , mark  208  is positioned in the vicinity of each intra-frame gap  124 . Also in accordance with the principles of the present invention, the film print  120  is provided with at least a second type of indicating mark, such as mark  207 , to indicate or identify locations where edits including cuts and/or splices may be safely or properly made. Locations identified as being appropriate for making a cut and thus amenable to subsequent splicing, which is typically a part of an editing operation, include a position at which the splice will not be projected onto the screen, or a position in the vicinity of inter-frame gap  128 . When cuts and splices are made at these latter positions, editing errors such as the generation of pseudoscopic images will be avoided and the existence of the correct stereoscopic pairs will be maintained. 
     In this exemplary embodiment shown in the figures, indicating marks  208  are provided in the form of bars or elongated strips alongside the gap and image(s) that the marks are protecting from a cut or splice. As such, these marks may be referred to as “warning bars”. Each intra-frame gap  124  on the film is provided with indicating mark  208  alongside and in close proximity to the gap, while avoiding placement of the mark in the viewable area of the associated image or images. Each mark  208  thereby defines the presence of images in the same stereoscopic image pair because the mark  208  is located in the vicinity of the intra-frame gap between the two images in the same stereoscopic image pair. 
     In some exemplary embodiments, it is possible that indicating marks  208  are provided at some, but not all, intra-frame gaps  124 . For example, marks  208  may only be provided at or near the beginning and ending portions of each film reel, where splicing is expected to be performed by a theatre upon receipt of a film shipment. In this latter example, individual reels of a film are spliced together to build up a single continuous film stored on and played from a large film platter. 
     Each indicating mark  208  has a length at least equal to the gap width of intra-frame gap  124 , i.e., at least co-extensive in length with the gap width. Generally, mark  208  is produced to extend beyond the gap width so that it is also adjacent to a portion of one or both images in the stereoscopic image pair. In some instance, mark  208  can be considerably longer so that it is as long as the four consecutive perforations. For this latter example, mark  208  would extend symmetrically alongside portions of each image on both sides of an intra-frame gap to cover a length of approximately two consecutive perforations (e.g., P 1  and P 2  in  FIG. 2 ) in each direction from the intra-frame gap  124  and this mark would terminate so that it does not impinge on or extend to the region near inter-frame gap  128  and indicating mark  207 . The use of perforations as a guide to mark placement can be better understood in the context of conventional editing practice. In editing of 2D films without marks or any such indicia, splicers (i.e., individuals skilled in the cutting, splicing, and repair of film) tend to make cuts in the film equidistant from two consecutive perforations adjacent to a gap between images in order to minimize weakening of the film by cutting close to a perforation. 
     It is not nearly as important to have the warning bars of marks  208  placed adjacent to images, even though locations where cuts should not be made include the image areas. Image areas are generally more easily discernable to experienced film splicers and film editors. Since film editing personnel are well-trained to avoid cutting through image areas, warning marks are deemed to be more necessary at and near the intra-frame gaps. 
     In the example shown in  FIG. 2 , indicating mark  207  is provided in the form of a triangle or an arrow pattern, in which the bright or white triangular portion identifies an inter-frame gap at which a cut and splice may be made. Indicating mark  207  may be provided for each inter-frame gap  128  in the film. But it should also be appreciated that, in the manner similar to that discussed above for mark  208 , it may be desirable to provide marks  207  for only a portion of inter-frame gaps  128  such as those at or near the beginning and end sections of a reel of film, where splicing is expected to be performed. 
     Inter-frame gap  128  on the film is provided with indicating mark  207  alongside and in close proximity to the gap, while avoiding placement of the mark in the viewable area of the associated image or images. Each mark  207  thereby defines the proximity of images belonging to different consecutive stereoscopic image pairs because the mark  207  is located in the vicinity of the inter-frame gap  128  formed between one image from one stereoscopic image pair, e.g., image R 1  from the (L 1 , R 1 ) pair, and an image from another stereoscopic image pair, e.g., image L 2  from the (L 2 , R 2 ) pair. 
     Indicating marks  207  are different in some visually discernible manner from indicating marks  208 . In some examples from experimental practice, it has been found that the use of orthogonal marks has been useful. One exemplary set of orthogonal marks is shown in the figures in which mark  207  is oriented in a substantially perpendicular direction to indicating mark  208  so that one mark appears wider than it is long while the other mark appears longer than it is wide. These types of marks may also be viewed as being complementary. Regardless of the terminology used, it is important to realize that the two marks should be discernibly (or visibly) different. Moreover, when portions of these marks are joined together by an incorrect cut and splice operation, the resulting mark should be discernibly different or distinguishable from marks  207  and  208 , as discussed in conjunction with  FIG. 3 . 
     Since both tick marks  207  and warning bars  208  are located outside frame boundaries defined by rectangular areas  205 , these indicating marks will not be projected onto screen  150  during a normal presentation. Furthermore, by providing these marks inside the boundaries defined by edge limits  206  away from the edges of the film print  120 , the indicating marks will also not interfere with any ancillary information on the film including optical soundtracks  201 ,  201 ′, and  201 ″. 
     Indicating marks  207  and  208  may also be printed in different colors to improve their detection, whether the detection is done by an automated machine or by a human. For example, tick marks  207  can be written in a green color and warning bar  208  can be written on the film in a red color. This color combination has a universal meaning that can be used herein to more clearly define regions that are respectively safe and unsafe for cutting and editing. 
     Indicating marks  207  and marks  208  are shown in the figures as being centered or positioned symmetrically with respect to respective inter- or intra-frame gaps. In other exemplary embodiments, one or both of marks  207  and marks  208  may be positioned in an asymmetric manner with respect to their associated frame gaps. Asymmetric positioning may result in a longer or larger portion of an indicating mark being positioned above a frame gap than the portion of the same mark positioned below the frame gap. 
     Once the splicing and editing of the film is complete, it may be necessary to perform an inspection of the film to check for editing errors or to perform additional quality control operations. The presence of indicating marks  207  and  208  are believed to be useful in these operations. For example, in a case where indicia or indicating marks  207  and  208  have been ignored and an improper cut and edit—such as cutting at least one warning bar  208 —has been made, the resulting splice can be examined for correctness and validity. As used herein, a splice is considered “valid” when the images that are spliced together correspond to images meant for different eyes, even though these images do not necessarily belong to the same stereoscopic image pair for the same scene. If the splice does not include a warning bar  208  or some portion thereof, then the splice represents a valid splice, and indicates a valid stereoscopic sequence. Such a validity check assumes that the cuts have been done in the vicinity of a gap region, whether at an inter-frame gap or an intra-frame gap, and not across an image area where a warning bar  208  is absent. If the resulting mark at the splice includes two halves or two portions of different warning bars  208 , such that the resulting film appears to have a single warning bar  208  marking the region that spans the splice, it also represents a valid splice, and indicates a valid stereoscopic sequence. Such a splice is considered valid in this particular context because the two images spliced together are associated with different eyes. 
     Splices can occur for a multitude of different reasons. For example, a splice may arise from an improper cut at a warning bar  208  that is subsequently spliced back together when the mistake is realized. Another type of splice may arise from an improper cut of the film, that is followed by splicing two unrelated images such as right- and left-eye images from different pairs of stereoscopic images, e.g., representing different frames or scenes. In this case, even though the two spliced images do not form the same stereoscopic pair for a particular frame, at least they will not result in pseudoscopic images when they and subsequent image pairs are projected. Generally, any adverse effect arising from viewing two unrelated images is likely to be transient in nature lasting usually for only 1/24th of a second or so. 
       FIG. 3  shows an example of an invalid splice, in which the composite mark  309  includes portions of each of the two original marks  207  and  208 , yet is a completely different indicating mark itself. Composite mark  309  is shown in  FIG. 3  as including a portion  307  of a tick mark  207  and a portion  308  of a warning bar  208 . It is clear that this type of invalid splice results in two right-eye images  350 R and  360 R being adjacent to each other. The alternating pattern of left and right images is thereby disrupted. Thus, the splice  321  in film  320  is invalid and will corrupt the stereoscopic presentation when projected. It will be appreciated that when indicating marks  207  and  208  are positioned symmetrically with respect to their respective inter- and intra-frame gaps, and when the cuts are also made symmetrically at the gaps, then composite mark  309  will include half of indicating mark  207  and half of indicating mark  208 . 
     Tick marks  207  and warning bars  208  not only serve as indicators for locations at which cuts or edits may be made or should not be made, but they can also be used as an inspection tool to provide a rapidly observable determination about whether an edit or splice in the stereoscopic film is valid. Although indicia  207  and  208  are shown as tick marks and warning bars, respectively, in the examples shown in the figures, it is contemplated that different designs or other patterns may be used to provide visually distinctive and discernible indicating marks in accordance with the principles of the present invention in order to facilitate inspection, film editing, splicing, and/or quality control tasks. The indicating marks may also be written as machine readable patterns, shapes, or codes. 
     The present invention provides a method and system suitable for use in film production, editing, and inspection, in which a film is provided both with at least a first type of indicating marks to indicate or identify location(s) where it is not suitable to perform a cut or edit, i.e., where cuts or edits are disallowed or should not be made; and a second type of indicating marks to indicate location(s) that are appropriate for making cuts or edits. The first type of marks should be sufficiently different from the second type of marks so as to allow for ready visual distinction during editing and/or inspection tasks. In some applications, it may be sufficient to provide a film with only one type of marks, e.g., the first type of indicating marks to identify a “no cut” zone, or the second type of marks to identify a “cut” zone. For example, in situations where the “cut” regions are readily identifiable by existing procedures, it is sufficient to provide only the first type of marks to indicate one or more “no cut” regions. In the scenario of having only one type of marks, an invalid splice will include only half of the indicating mark (as opposed to a composite mark containing portions of both types of indicating marks). 
     These marks may be written onto the film at any appropriate stage during film production or printing, e.g., using a film recorder. Furthermore, these marks may be used in quality control and inspection operations—whether done manually or in an automated manner—to indicate whether a splice is valid or proper, in which these operations are based on the types of composite or resulting mark found at a splice location. In the case of an automated method to perform splice inspection, a processor may also be configured or programmed to detect an invalid splice and to provide a warning in the event that a bad or invalid splice is found. 
     A system and a computer readable medium are also provided for implementing the method of the present invention. For example, the system may include one or more processors, memory devices and so on, and the computer readable medium may be programmed to contain instructions for implementing various steps related to the method of the present invention. 
     Although the principles of the present invention are illustrated above with examples for 3D projection, they can also be applied to 2D films such as a television or movie film or the like. The presence of a sequence of nighttime images, which would appear light in a negative, does not allow one to see a discernible gap between the images or frames. In the event that a splice should be required in such a nighttime sequence, the editor would experience significant difficulty in locating the inter-frame gap between consecutive or adjacent images, thereby making the cutting and splicing operation very difficult. In this case, a series of alternating indicating marks alongside the corresponding image regions (e.g., a first type of marks for indicating “no cut” regions) and gap region (e.g., a second type of marks for indicating “cut” regions) could prove invaluable in speeding up the editing process while affording a concomitant increase in the likelihood that the cut and splice will be performed correctly. In the case of a 2D film, the inter-frame gap is the only type of gap existing between adjacent images (i.e., intra-frame gap does not exist). 
       FIG. 4  illustrates an example of a portion of a 2D film negative  400 , having a plurality of images  401 ,  402  and  403 , with any two adjacent images being separated by a corresponding inter-frame gap  410 . One or more indicating marks  408  (shown as dark lines in this example) can be provided along at least one side of one or more images for indicating or identifying corresponding regions that are not suitable for performing a cut. For example, some or all images on the film can have respective indicating marks  408  extending along most of the side (or length) of the corresponding images. Furthermore, one or more indicating marks  407  (shown as dark triangles in this example) can be provided proximate or alongside the respective inter-frame gaps  410  for identifying corresponding regions in the film that are suitable for performing a cut and/or splice. In this example, one indicating mark  408  is positioned alongside or adjacent to image  402 , and another indicating mark  407  is positioned alongside a gap  410  that is adjacent to the image  402  (e.g., one mark  407  is alongside a gap  410  that is before image  402 , and another mark  407  is alongside another gap  410  that follows image  402 ). 
     It will be understood by persons skilled in this art that the indicating marks taught herein can be written onto the film at various stages in the film production process. Obviously, a camera recorder can be adapted to write each type of indicating mark. Furthermore, during the production of a conformed negative, each indicating mark could also be written onto the film. Other stages in film production may also be more or less adaptable to the writing of these indicating marks. Writing techniques are well known in the art and are not described herein. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the present principles and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. 
     Moreover, all statements herein reciting principles, aspects, and embodiments of the present invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, including any elements developed at any that perform the same function, regardless of structure. 
     A number of implementations have been described herein. Nevertheless, it will be understood that various modifications may be made. For example, one or more elements of different implementations may be combined, supplemented, modified, or removed to produce other implementations. Additionally, one of ordinary skill will understand that other structures and processes may be substituted for those disclosed and the resulting implementations will perform at least substantially the same function(s), in at least substantially the same way(s), to achieve at least substantially the same result(s) as the implementations disclosed. In particular, although illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present principles is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present principles. Accordingly, these and other implementations are contemplated by this application and are within the scope of the following claims.