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Author Topic: ID Frames and their effect on Sound Mathew Molloy Master Film Handler Posts: 357 From: The Santa Cruz Mountains Registered: Nov 2000 posted 02-04-2003 02:39 AM                     Mark Wrote (When you do changeovers, how is this compensated for, do processors fake a slight fade between the two sources, or does the sound jump right from one reel to the next?) The sound does changeover from one reel to the next at exactly the same time the picture does. Unlike a splice with missing frames and the sound jumps nearly a second later. Therefore, even a mildly poorly accomplished reel change will appear natural. As far as ramp up speed and timing; it's all based on how well you know your machines and how the cues are 'timed'. What I mean is that a film that is cut right has a certain beat to it when the reel change happens - you can feel when you need to hit the c/o button and voila! As much as I love running changeovers, a plattered presentation missing ZERO reference frames is the way to watch a movie.  |  IP: Logged Duncan Smith Film Handler Posts: 50 From: England Registered: Jan 2003 posted 02-04-2003 01:16 PM                     I run 35mm changeover and also from a tower. With the amount of films I have moving through my projection box I would be completely lost without an ID frame at each end of the reel. I can't tell you how many times I have received a print with the wrong leaders attatched and in the wrong cans. If I assumed they were correct then I would have had far worse problems to contend with than 2 frames lost; more like 15 minutes while I try and put the film back in the right order following advice from a luckless customer who has seen the film before. If I don't find ID frames on the leader I call the distributor to get an ID on each reel, this has paid off more than a few times. I know it's regretable to lose any amount of image or sound content but the alternative is far worse. No-one ever asked for a refund or had a show cancelled because of a couple of frames at the end of a reel were missing (I hope not anyway). Unfortunately this is the real world we live in where some people do not consider the full implications of what they do when making up a feature onto a cakestand or tower and those of us who proudly run changeover are left hanging. It would be great if practises were agreed upon and maintained to everyones advantage. (I'll take off the rose tinted glasses now).  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-04-2003 02:02 PM                    Analog changeover switching is done by the pre-amp card of the processor. I've never heard of one that does anything other than an instantaneous change but I suppose such could exist but I don't think a crossfade would be desirable since it's supposed to be just like a straight cut edit. By instaneous I mean instant when signalled. That signal may coincide with with the picture changeover but it need not be. My booth has separate buttons for picture and sound changeover so while they are normally operated together it is possible to change picture while hanging on the old reel's sound to finish a syllable.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 02-04-2003 02:18 PM                        In some older installations (like the Grandview Drive-In where I worked as projectionist 1967-1970), the sound changeover was done by switching between the exciter lamps on the two projectors. The lag of the heavy filament exciter lamps gave a natural "cross-fade" between the reels.  |  IP: Logged Mathew Molloy Master Film Handler Posts: 357 From: The Santa Cruz Mountains Registered: Nov 2000 posted 02-04-2003 02:18 PM                     My Seattle booth (The Egyptian) had just that, seperate buttons for the audio c/o and the dowser. We also had a three-position switch for the sound format for each machine. (This was run as a festival booth quite often and shorts packages would go from one format to the next, to the next, to the next.) I remember a couple times prefering to do one ahead of the other, but I don't remember why now. Perhaps I was just being 'artsy'. I do remember an instance where I realized at the end of one short I started the next short a little too early (during the end credits of the current short) so I changed the sound over to catch the opening of the next short followed by a 'crossfade' with the hand dowsers. Looked quite nice, actually.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 02-04-2003 02:19 PM                        Don't forget places that use exciter-lamp changeover systems, where the sound does a quick fade-out/fade-in at each changeover. Some places feed a very small amount of current to the "idle" exciter to keep the filament warm enough to just barely glow, which allows it to come to full brightness rather quickly, making the sound dropout less noticeable. Having separate picture/sound changeover controls is nice, but that seems uncommon in the New England area.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-04-2003 02:28 PM                     Missing frames when building prints is definitely more of an issue than running on changeovers. The guys at the labs who are QCing the prints don't ever buildup the films and only see clean starts and stops. This is the same problem with so many policy trailers, where the audio starts in "dirty black" or in the countdown leader. No one ever remembers that easily over 95% of all films will have their leaders removed for projection, and in turn they never pay attention to the fact that the audio is ahead of the picture.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-04-2003 04:04 PM                    I remember once long ago being confused by the way an exciter lamp C/O circuit was wired in an ancient booth, that is, until I realized how elegantly simple it was. One side was a SPDT switch (regular electrical hardware type, sold as "3-way") with the DC fed to the pole and the two "throw" lines eventually leading to one and the other bulb...send power down one line or the other to select the projector. But first the two wires pay a visit to the other position where there is a DPDT switch wired in what might be called a polarity reversing configuration (electrical hardware switches expressly designed to do this are sold as "4-way" switches). This has the effect of either passing the power along on the same wire or flip flopping the lines to invert the selection made by the other switch. So flipping either switch changed which exciter was on. No muss, no fuss, no relays.  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 02-04-2003 04:52 PM                     Just ran sneaks of Far From Heaven last weekend. The change from 2 to 3 has a guy talking going right through the changeover. If ID frames had been removed on building the print, there's no way that reel change would have worked. When building and not leaving ID frames, I make sure the print is well identified by black marker on the edges of the film on both the print and the leader. It's tricky getting such small writing happening, but you get used to it. I used to leave an ID frame, but then I tried it without... I'd never go back.  |  IP: Logged Karen Hultgren Master Film Handler Posts: 492 From: Agoura Hills, CA, USA Registered: Mar 2000 posted 02-04-2003 07:37 PM                        Because DTS matches analog frame to frame, we have superior editing capabilities. Any size edit is seamlessly accomidated by DTS (as long as all discs with the needed digital audio are loaded). That is why DTS is most often used during the Academy sound "bake-offs" (for sound academy award nominations). We have looked at "basement" readers and found them not feasible. You never know, though, we might incorporate them in future products. Karen at DTS khultgren@dtsonline.com  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 02-04-2003 08:57 PM                        Would DTS even really benefit from a basement reader? The only advantage that I can see for SRD is that threading the cat. 699/700/701 takes a few extra seconds. The DTS reader is so easy to thread (and nearly impossible to thread incorrectly), that I don't really see the point, except maybe for installations that use enclosed reel magazines (and which aren't likely to have DTS, anyway).  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 02-04-2003 09:59 PM                    quote: If ID frames had been removed on building the print, there's no way that reel change would have worked. I'm thinking that in cases like that, a change over would be almost impossible to pull off correctly.... consistantly. Maybe I'm wrong, but it just seems like way too many things (some of which are out of your control) that have to be in EXACTLY the right place at the right time. [ 02-06-2003, 08:11 AM: Message edited by: Mark J. Marshall ]  |  IP: Logged Ray Derrick Master Film Handler Posts: 310 From: Sydney, Australia Registered: Sep 2001 posted 02-09-2003 06:12 AM                     I agree with Steve AND Brad. You can't tell by looking at it AND chopping a frame off the front of an audio "rise" will usually be audible. In fact you can clip substantially less than a frame and still hear a noticable cut-in on most audio material. Regarding analog audio offset, if a film is correctly laced it will be perfectly in sync for audients sitting precisely 45.83333 feet back from the screen speakers (that's just under 14 metres for those living in enlightened countries). And anyone sitting 91.6666 feet back will hear the audio exactly one frame behind. Our brain is less critical of an audio lag than a lead, so a one frame lead and two frame lag is about the limit of our tolerance for lip sync. So even in the largest indoor theater, the sound will appear in sync at the very back (provided the film is correctly laced). But the important thing is that the bigger (longer) the theater, the more critical you must be of the picture-to-audio lacing offset.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-09-2003 08:25 AM                    Let's say Moses supposes he wants to thread up non-erroneously and suppose that Moses takes into account the size of his theatre and a 1 frame-early sync built into the track but how do you suppose Moses should determine the picture position? Just before pull-down, just after, or in the middle of the stationary dwell period?  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 02-09-2003 09:28 AM                     That's of course a function of how Moses threads: the position of the intermittant at the time the constant-speed sprocket driving the film through the soundhead starts moving. Let's assume that Moses threads by setting the intermittant to be right at the start of the dwell period ("just after pulldown"), because that's how people thread. Also assume that the "sound of one frame" should be heard starting 1/2-way through the pulldown to the frame, throughout the frame, and then ending 1/2-way through the pulldown to the next frame. We can conclude Moses is 1/2 of a frame (2 perfs) further along than he should be, so to compensate for his threading he should tighten the sound loop by two perfs relative to the position of the diamond. Of course, if Moses threads out-of-frame and then cranks the framing knob...well, someone's gotta deal with that red sea runoff. D'you suppose he filed an EIS? --jhawk  |  IP: Logged

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