The Optical Barrier

Crossing the Line

A great subject for film buffs this one. It’s so simple, but it catches us all out at some time. It’s just a matter of helping your viewer tune in to each new shot as quickly as possible. If your cuts are invisible, he or she will be able to get on and enjoy the story. If you confuse him he’ll probably get fractious. And if he’s watching television he might reach for the remote… You’ll hear directors talk a lot about “crossing the line’ or the ‘optical barrier” and it all sounds jolly mysterious. Actually it’s not at all complicated in principle. Remember the hat owner and the nose proprietor? Here they are again:

They’re looking at each other. Or to be more exact, one is looking left and the other one right. So they appear to be looking at each other. It’s more or less how you’d see them with the eye.



The camera positions would be like this:

It’s easy if the shots are taken in the same shoot, but it isn’t always that simple. Even if the man was speaking on the telephone in one country and the girl was speaking to him (in reality or pretence) five thousand miles away, you still need one facing right and the other left. And by the same token it’s possible to shoot the two people in rooms with similar decor in two separate continents a month apart and to cut the two shots together so that it seems a perfectly normal scene. As long as one looks left and the other looks right it will work just fine! But here they are once more both looking the same way – it’s as if they”re both looking at a third person:




The camera positions would have been like this:

All you need to do to avoid this rather elementary mistake is keep the camera on one side of the line or the other for all shots in any sequence. Sounds complicated but another way to think of it, if imaginary lines through the head aren’t your cup of tea, is to think of looking directions. In the earlier example, when he was looking right (from the camera’s point of view) and she was looking left, everything was OK. But if they both look right the two shots won’t cut properly together. When you’re shooting two people talking to each other (whether it’s an interview or a major drama) if one looks left, the other must look right.

Car Chases

There’s a similar sort of problem when you”re shooting any means of travel. If a car is going from left to right in one shot, it should continue that direction of travel in the next. If a man is walking from his front door to meet a friend and he”s going right to left, then when we see him arrive at where the friend is standing, he should still be moving right to left. It”s even more important to be careful about direction of travel if you”re shooting a chase.   For example, can you imagine these two shots cut together?
One car is going left to right, the other right to left. The implication is obvious; they’re going to have a head-on collision! The camera has crossed the line again. There are exceptions to this rule about not crossing the line (television and film are full of exceptions to almost every rule). Imagine you”re shooting a comedy, and you want to show that a driver is lost and can”t find his destination. You might well have a series of shots showing him going left to right, then right to left, then left to right, towards camera, away from camera, etc. – he’s effectively driving all over town in his search for whatever it is. A non-exception, but worth mentioning: If you did want to shoot the car chase, and wanted it to last perhaps four minutes, it would be very boring if the cars always went left to right. And some lighting set-ups or physical road set-ups might demand a right to left shot. No problem.




There are many ways to make a car change visual direction.

Here’s one way to do it in the middle of a shot:

Actually, a car chase (or any other kind of chase) would be boring if every shot showed the action going left to right, left to right, left to right, and so on for ever. So shoot with variety in mind. Have maybe four shots left to right, then one of the car going right and towards the camera (on a corner?) turning off left at the end of the shot, then three shots right to left, then a shot from the chasing car (more jargon: the driver”s point of view – POV) looking straight ahead; then you can go back to left to right travel for a while. Etc., etc. Be very careful, though, of your continuity if the car chase gets at all rough. The self-repairing cars and jumping hubcaps in Bullit are truly wonderful! Here’s another sort of exception. Imagine these two shots cut together.
Technically the cut crosses the line, but the geography is so well-defined it will probably be OK. You would get away with it if the plot had established that there were only the two people on location or we’d seen another frontal shot of them walking to the beach so we know what they look like. But if these were the first two shots of a film the implication could easily be that the second couple were watching the first. Make sure the pictures tell the story you want to be told.

Truth is Beauty, therefore Beauty is Truth

Often a “real” shot will not be very pleasing. Imagine a scene outside a building. You”re doing a piece on car parks so you shoot an interview with an irate car driver using cars and trees as the background. Now look at the reporter/interviewer; his real background is probably the blank white wall of the building. Not a very pretty shot, and it contrasts hugely with the master shot. So cheat it – move the interviewer round so that you”re shooting against cars (different ones from the interviewee”s shot, of course), then move the interviewee to give the interviewer an eyeline just off camera. Looks much better, and “true-er” than the “real” shot! Had enough of optical barriers for now? OK, just don”t let it confuse you. The main thing is, if the one person looks to the right of the camera, the other should look to the left. Don”t worry at all about real geography, just about how it will seem on screen. The joins between pictures are just as important as the pictures.