rule or heuristic?
Walter Murch, identifies and prioritizes six criteria for the ideal cut. (Murch, W. 2001:18)
- Eye Trace (Described also as Gaze cues (Smith, 2005))
- Two dimensional plan of the screen
- Three dimensional space of action
Interestingly, the 180 rule in filmmaking (where the camera remains on the same side of a axis of action, typically between two people), is most closely related to Eye trace and the 3 dimensional space of criteria. While suggesting that it is best to achieve all the criteria, Murch is clearly identifying which should be maintained at the cost of the others. This reduces the 180 degree rule to a heuristic; a rule of thumb. If course, there may be (and are) other ways to establish and support the diegetic 3d space of the film for the viewer
There is an interesting departure from the 180 degree heuristic at the end of Casablanca. (Curtis, 1942) You can see the scene in context at https://youtu.be/KtiMG23ZVps and the time references below relate to the time into the linked clip in minutes and seconds.
That’s all over a long time ago: 2:41. Rick has obtained the signed letters from Captain Renault the axis of action runs from the background right to the foreground left through the two actors.
Here it is: 247. This shot is on the other side of the axis, not following the heuristic. In this shot, we see the exchange of papers , a handshake, and several facial expressions and glances. It is followed by a jump back over the access to:
This scene is driven by emotion and story and rhythm. Showing the exchange of the papers might have been attempted by extending the scene before (I understand) to show the transfer over the shoulder. However, this would not have been able to show the body movement, gesture, expression, and handshakes of both men which is important to the story, to the resolution of their relationship, and the emotion of the scene and continuing the OTS shot would have failed to bring Ilsa’s highly emotional performance back into view.
I’ve never heard (and do not expect to hear) anyone speak up to criticise this scene. Indeed, I expect that few if any viewers see the cut or are taken out of the moment by the cross over the axis. Many people will report this as one of the most emotional moments they have encountered in film and it is a perfect example in support of Murch’s priorities. It is also an example that supports an attentional theory of cinematic continuity. Viewer’s attention is highly focussed on the men’s faces, their handshake, and Ilsa’s sob. The shift of gaze is used several times to prime saccadic eye movement to an off screen target that will be cut to momentarily (so we know that viewers who anticipate will be effectively blind for about .15 seconds and will not see the cut about to be made – more on this below). Finally, their mise en scene, the constant gazes, and the cross axis cut serve to provide a spatial metaphor of them as a triangle. This is surely an intended purpose and the cross-axis cut is essential to this purpose at the same time that it is well hidden in several ways. Not only does the audience not get lost in diegetic space, but that space is used to reinforce a central point about these three as a triangle. March’s criteria are all fulfilled (and expanded on) without the 180 heuristic. Indeed, ‘breaking’ that rule was necessary for the outcome.
On the gazes in this scene
There are several ways in which our eyes move. They can pursue an evenly moving target slowly if such a target exists or they can reorient quickly (saccade) to locate a new target or to catch up with a faster target. They also have a vergence movement when we converge our view on a close object. There are also smaller movements: nystagmus( a very small but constant tremor), drifts, and microsaccades (which occur when poor motor control causes view to drift and is suddenly corrected) (Rayner, 1998). Of significant interest to a discussion of editing are the saccadic eye movements
Saccadic eye movement, Saccadic suppression and edit points
Saccadic eye movements occur several times per second. They are very fast, reaching a speed of 300 degrees of rotation per second and hence they are also brief (20-50ms). However, a process of saccadic suppression prevents us perceiving before (about 75ms) during, and after (50ms) this would add up to approximately 0.15 seconds and is comparable to blinking in duration. One amusing experiment you can do is to look in a mirror attempt to alternate your gaze quickly from eye to eye. You will notice that you can watch someone else do that and see their eyes move but you cannot see your own eye motion. (Smith 2008). So a viewer is blind for a significant period of time between fixations which last approximately .3 seconds when viewing a scene (Rayner, 1998). At these rates, you are not visually perceiving the world around you for about 20-30% of the time.
Creating saccadic eye movement
Fixations are the result of attending. So you might saccade between letters and words while reading (there is much research on this available), you might saccade towards the location of a sudden sound as part of an orienting response, you might saccade to follow the gaze of another person towards the person or object they are viewing, or you might simply follow an arrow or someone pointing. A gaze cue is seen in the Casablanca clip referenced above.
At 2:39, Rick turns his gaze from Victor to Ilsa and this is immediately followed by a cut which the viewers would have expected. Form many viewers, this might prime a saccadic eye movement from Rick to the left. and the cut should occur in about a tenth of a second.
Even prior to this example, the three have been glancing off screen to maintain the viewer’s ability to keep their spatial relationship in their mind’s eye. It is the gazes that establish both the space and the rhythm with (or without) the cuts which are mostly likely invisible. It may be that mixing cuts and non-cut periods of gaze exchanges further serves to further hide the cuts. It is also likely that the constant establishment of their spatial relationship improves the viewer’s mental model of the space in a way that lets them orient across the axis crossing discussed above with ease (rather than notice the cut.
Curtiz, M. (1942) Casablanca. Warner Brothers
Murch, W. (2001) In The Blink Of An Eye. Ed 2 USA: Silman-James Press
Rayner, K. (1998) Eye Movements in Reading and Information Processing: 20 Years of Research. Psychological Bulletin,1998, Vol. 124, No. 3, 372-422
Smith, T. J., Henderson J. M. (2008). Edit Blindness: The relationship between attention and global change blindness in dynamic scenes. Journal of Eye Movement Research 2(2):6, 1-17