double Cue dots break:

They are still used of course. I've never been sad enough to time them but there's usually one a certain time before the reel change and then one at the changeover point. I don't know if they do the changes on the hoof or whether they stick all the reels together but there's always a bit of a picture jolt at the changeover

The first set (they're usually marked on four successive frames) are at 8" to the changeover, and are known as the 'Motor' cue - i.e that's the point that you start the second machine, having placed the correct frame of the Academy leader in the gate.*

The second set are the 'Over' cue and are 1" back from the end of the reel. These indicate the right time to hit the changeover button to the second machine. A moment too soon and you clip the soundtrack, a moment too late and you stand a chance of getting the tail of the reel going through the gate.

Since the 1960s projectors have had larger spool boxes so it's very unusual to run 2000ft (20 minutes) spools individually. These are normally joined up in threes on 6000ft spools, giving a run time of around an hour. If a cinema is still using changeovers (and quite a substantial minority of independants do - as well as places like the NFT running valuable archive stock) the average feature will now include only one changeover. The vast majority of cinemas now use a non-rewind system such as a Tower or a set of Platters (a 'Cakestand') to run entire programmes with no changeover required.

S

(* As it's over a decade since I worked in the industry I can't actually remember what number should be in the gate as we only ever did changeovers for press shows or the odd one-off screening. The numbers are placed every 16 frames and relate to feet of film - they only work as seconds markers when you're running a silent film at 16fps!)

Interesting Steve, thanks

How is the actual changeover done? Is it 2 projectors pointing at the same screen (or a system of lenses combining the 2) or does the second reel just get fed through the same path as the first reel?

It's two (occasionally three as at the Odeon and Empire, Leicester Square) identical projectors with optical centres radial to the centre of the screen - which itself is usually, but not always, concave. Each machine is equpped with an electro-magnetically operated 'zipper-shutter' which is usually at the back of the mech between the light source and the shutter. The changeover system ensures that only one zipper is open at any one time, and that the audio signal from the correct machine is routed to the sound processor.

You press the changeover button on the incoming machine, and this operates the correct solenoid to close the zipper on the outgoing machine, and usually switches the sound as well, although some machines used a separate sound changeover switch.

The outgoing machine then needs to be stopped and the light source (usually a Xenon arc-lamp, but occasionally still a carbon arc) extinguished. There's no rewind facility on a cinema projector, so the take-up spool needs to be taken off and put on a rewinder - either motorised or more usually manual - where there film is rewound and checked at the same time to ensure no broken sproket holes, tears etc.

Of course, with more and more cinemas moving over to digital projection, and the amount of 35mm film stock being run diminishing year-by-year, this is all a rapidly dying art. I think I left at the right time before all the fun had gone out of it, but it will be a sad day when "going to see a film" doesn't involve watching an image on a screen created by shining a bright light through a strip of celuliod tri-acetate... or polyester!

Have you ever seen a xenon arc lamp implode?

Scary biscuits.

(we're going wildly off topic here, I know...)
Though you still get cigarette burns every 20 minutes, don't you?
I can't remember what first drew me to their attention - but I think they get a mention in Fight Club .

You do - because film is still delivered in 2000ft reels. They've only ever been called "cigarette burns" in Fight Club though - the book apparently invented the term. To projectionists they're "cue dots" or "changeover cues".

S

I can't stand a TV picture that has the edges cropped. Any computer with a TV capture device installed always
displays the full picture, without any overscan, regardless of the whether pictures are delivered in 16:9 or 4:3,
or viewed on a CRT or LCD monitor. Exceptions to this ... any digital STB with 16:9 mode is on, which creates
an overscan that cannot be removed or reduced, or the WMV based downloads and Flash based streams
on BBC iPlayer which have always appeared to have had some unnecessary overscan artificially added.

(The last example could be a bug they may be unaware of in the transcoding software they use.)

I set up my TV's gradually reducing the overscan until the very edge of the picture comes into view on either
side, top and bottom. Now that you mention it, using a 16:9 testcard and PLUGE would have made it easier.


I think perhaps the discussion about overscan, (if we're going to discuss it any further) merits having its own
thread and could do with being split off, so this thread can continue back on its original topic of cue dots.

It's your telly; you are perfectly at liberty to set it up how you want. I was simply challenging your assertion that


Overscan is not intended to be seen, no matter what a capture card offers you. Any cameraman, director or engineer working in TV will tell you that.

Hmm - how do you deal with 720x576 sources then?

The 16:9 or 4:3 area is the central 702x576 image area (designed to correspond to the 52us analogue active line time when sampled at 13.5MHz) - not the 720x576 image area which is wider than 16:9 or 4:3 to avoid cropping slightly mistimed signals. These 18 samples (9 each side) are not designed to be seen - and some digital platforms only send a 704x576 signal (the nearest MPEG2 multiple) as a result.

If you see a 720x576 version of Testcard W you'll notice that there are arrow heads that meet close to the edge of frame. On a correctly aligned display with no over OR underscan you should see the arrow tips touching the left and right of frame but NOT the short bits of the tips they touch (which are in the 9 extra samples each side) IF the top and bottom of frame fills the screen but isn't cropped. If you can see the whole width of the image (including the partial arrows on the extreme edges) you will need to have a small amount of black top and bottom of frame otherwise you will be horizontally squeezing the image a little -as the 720x576 signal is wider than 16:9.

Also almost any SD studio source will have slightly ragged left/right edges that are most definitely NOT designed to be seen due to timing issues (most cameras use analogue component triax). Similarly there are half/full line issues at the very top and bottom of frame that are also not designed to be seen, however with letterbox presentation it is sometimes impossible to avoid this (though many letterbox sources will crop the top and bottom half/full line to avoid this)

Overscan is there for a reason - directors and camera people frame for it - and hope viewers are watching with it - particularly in SD...

There are professional reasons to monitor an underscanned image, and personally I reduce the overscan on my TVs to the minimum I feel acceptable. However I don't remove it completely, as the timing errors, blanking edges moving, DVEs and other transition devices dropping in and out can be distracting...

I was at the Prince Charles Cinema in London last night, where their very old and scratchy print of It's a Wonderful Life got caught in the projector, and the film melted up on screen. Something I'd never seen before in real life, and something my dad reckoned he'd not seen since the 60s.
(Thankfully, they still have a projectionist who knew what he was doing, and it was back up and running again in minutes.)