Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site qubix.UUCP Path: utzoo!watmath!clyde!burl!ulysses!harpo!decvax!decwrl!sun!qubix!msc From: msc@qubix.UUCP (Mark Callow) Newsgroups: net.video Subject: Re: PAL <==> NTSC (& Movies) Message-ID: <1003@qubix.UUCP> Date: Sat, 14-Apr-84 20:26:32 EST Article-I.D.: qubix.1003 Posted: Sat Apr 14 20:26:32 1984 Date-Received: Sun, 15-Apr-84 08:25:21 EST References: <7019@decwrl.UUCP>, <988@qubix.UUCP> <236@hou2g.UUCP> Organization: Qubix Graphic Systems, Saratoga, CA Lines: 43 Conversion of films to TV is nothing like as hard as converting NTSC signals to PAL signals or vice-versa. A flying-spot telecine machine is used. This has a "projector" half and a "camera" half. The light source is a CRT (hence the name flying-spot.) scanning just like the TV set. The "camera" used to be a photo-multiplier tube. I don't know what they use these days. By varying the geometry of the image on the scanning CRT all kinds of tricks can be pulled such as showing a cinemascope film without an anamorphic lense. I can't remember exact details of this right now but I once saw it done at the CBC studios in Montreal. Since the film was shot at 24 frames/s and the TV is scanning at either 25 or 30 frames a second, depending on country, various tricks must be played to synchronize the two otherwise you get horizontal black bars moving down the picture. Where TV is 25 frames/s they simply speed up the film. This results in a 100 minute film only lasting 96 minutes. Other than that the speedup is imperceptible. Where TV is 30 frames/s the projector is gimmicked to show every fourth frame twice so that 30 pictures are presented to the TV every second but the film moves at an effective speed of 24 frames/s. Also frame shifting is synchronized with the vertical blanking interval. I have seen "telecine adaptors" advertised in Video magazine. These consist of a box with a hole at one side through which you point your projector. Inside there is a mirror that projects the image onto a ground glass screen at which you have your TV camera aimed. These are a crock for anything but slides. Without the proper synchronization you will get a flickering image with large horizontal lines running up the picture just like you get when you film a TV screen with a movie camera. Seeing an ad for junk like that in what I thought was a reputable magazine makes me wonder about the objectivity of said magazine's test reports. -- From the Tardis of Mark Callow msc@qubix.UUCP, decwrl!qubix!msc@Berkeley.ARPA ...{decvax,ucbvax,ihnp4}!decwrl!qubix!msc, ...{ittvax,amd70}!qubix!msc "I'm a citizen of the Universe, and a gentleman to boot."