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Author Topic: RCA Photophone Laser Conversion Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 01-20-2003 08:20 AM                    and a red light source! If your exciter socket and slit lens are good and you have a power supply I'd go the conventional route for now and see what happens. You can always go red later.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-20-2003 09:40 AM                     "If this goes into a cinema it will not be there long as it will be upgraded within a couple of years of service" __________________________________________________________________ Actually, I think it'll be there quite a bit longer than a couple of years! Do you work for Uncle George or something? Mark @ CLACO www.clacoequipment.com [ 01-20-2003, 08:35 PM: Message edited by: Mark Gulbrandsen ]  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 01-20-2003 04:19 PM                     I have put a piece of red jell in between the white excitor lamp and the lens. It did not drop the audio level very much, but did turn the light on the film red. I did not have any cyan track film to try through. Has anyone else tried this, and what does everyone think of this as a "fix" on a tight budget?  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 01-20-2003 05:18 PM                     The red gell may work if the red transmission is 660nm +/- 20nm which is highly doubtful; the infrared output of a conventional exciter bulb would bleach out the gel in a short time so output would be unreliable. Kinoton has an economy retrofit kit for some of their projectors which use a halogen bulb ( very little drift over the life of the bulb ) and a dichoric filter to convert to 660nm red output as an option of using the Dolby DPN 32075 LED that most manufacturers are using or USL large red diode or Laser. Richard Fowler Kinoton America Inc.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 01-20-2003 08:27 PM                    Huh? I don't understand the point of filters, whether gel or dichroic. They reduce frequencies of light that are not going to be modulated by the cyan-only dye but is that going to increase S/N? I would think you can only do that by increasing red output not by decreasing other colors.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-20-2003 08:35 PM                     Steve, The halogen lamp would be designed for high output in that important 660nm wavelngth region, and the dichroic filter, if designed correctly, would only suffice to trim that a bit further on either side of the operating realm of the lamp and to bring it in to exactly the 660nm +/- 20nm wavelength. The system overall would work more efficiently that way. Mark @ CLACO www.clacoequipment.com  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 01-20-2003 09:56 PM                        Any red filter made of dye would be relatively transparent to infrared, and therefore ineffective in reducing the unwanted infrared sensitivity of the reader. They would also be prone to fading. A dichroic filter may be possible, but would likely be more expensive than red LEDs and not have the advantages of a reverse scan red LED reader. Here are the spectral dye densities of the dyes used in Kodak VISION Color Print Film 2383: http://www.kodak.com/US/plugins/acrobat/en/motion/products/curves/ti2397d.pdf You can see that 660nm is right at the peak density of the cyan dye, and that the film dye densities fall off in the infrared.  |  IP: Logged Paul Trimboli Master Film Handler Posts: 274 From: Perth Western Australia Registered: Dec 2002 posted 01-21-2003 07:18 AM                     I had thought of just keeping the normal optics, have not got the soundhead so I hope they are in good conditon. I know I can go red latter, just worries me if I can do it cheap though! I had thought of red filters, but thought of the problems as well. What kind of price in Australian $$ would I be looking at for a red light source as well as for a reverse scan reader with red LED?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-21-2003 09:48 AM                     Kinoton offers a dichroic filter slide projector styled excitor lamp as an option for there machine  |  IP: Logged Peter Hall Master Film Handler Posts: 314 From: London, UK Registered: Dec 2000 posted 01-22-2003 01:32 PM                        Mark - I agree that if the budget allows it a manufacturers (or third party kit for American machines) is the best option. However where the client is looking at a low cost retrofit kit (esp when they have a penthouse SRD reader and analogue is a back up) we prefer these lasers over the Jax Lite and the ASL laser. We've had bad noise problems on the Jaxlites in Kinotons, and the ASL laser doesn't live up to it's promoise of being operator changeable as the gain and HF change so drastically (or at least they should)  |  IP: Logged Peter Hall Master Film Handler Posts: 314 From: London, UK Registered: Dec 2000 posted 01-22-2003 01:33 PM                        Sorry - wrong link Try http://www.fproj.com/feature.htm Peter  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-22-2003 03:11 PM                     peter do they have the same uneven illumination that the Ernamann laser and the Japan one that CPI has exhibit in that with the SMPTE unifomity test film it graphs out like a bell curve. THE ACL is very smooth in my experience  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 01-22-2003 05:46 PM                    I'm still not clear on this. Is reducing light flux in the regions that will not be modulated by the cyan dye (whether IR or colors other than red) going to increase the signal strength? If the pickup is a solar cell then I can see how the unmodulated light is going to give...well, make that increase, since it's always there...the DC bias but that should have no effect on a transformer or electronically balanced solar cell preamp input.  |  IP: Logged

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