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Author Topic: Carbon Vs Xenon Robert E. Allen Phenomenal Film Handler Posts: 1078 From: Checotah, Oklahoma Registered: Jul 2002 posted 03-29-2004 11:49 PM                     Thanks for the tip Scott. The next time I get out of my rural area I'll look for some of the newer installations.  |  IP: Logged Warren Smyth Expert Film Handler Posts: 158 From: Auckland ,New Zealand Registered: Aug 2003 posted 03-30-2004 04:11 AM                     quote: occasionally have flicker issue The quality of Marble carbons used to be variable. Naturally all carbons have to be kept dry and we used to store packets on top of the warm valve racks, I still do in fact at home. I now use National and Loraine which are fine. Placing a few in the lamphouse (near the side door), provides quick access and helps to dry them out before they are used. Cycling carbons through in this way, reduces the possibility of flickering due to dampness. This isn't so helpful though if you are only screening intermittently. Interesting to hear complaints about low light level on some screens from xenons these days. I've seen some situations where the film looks as if it's been shot day for night, except for the hot spot at the centre. Carbons arcs may not have been perfect but I used to get brilliant results from 9mm and 10mm as well as 13.6mm rotating trims. 70mm really sparkled and was a real treat. It made all the cleaning and maintanence of arcs worth while although sadly, I appreciate the impracticality of them today.  |  IP: Logged Mattias Ohlson Expert Film Handler Posts: 180 From: Falun, Sweden Registered: Mar 2003 posted 03-31-2004 04:00 PM                     A newbee qustion. 1 What is the life expectancy range for a medium power xenon bulb? 2 What is the time carbon lighting lasts?  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 03-31-2004 04:10 PM                        A typical 2kw xenon bulb (for example) is guaranteed by its manufacturer for 1,500 hours of operation. The guarantee is significant, because a bulb costs US$300 plus to buy new. In reality, many projectionists apply tricks of the trade to make their lamps run an awful lot longer. In the last cinema job I had before moving to archives, I routinely expected to get double the guaranteed hours (i.e. around 3,000) out of each lamp before it started to flicker and needed replacing. The act of striking a xenon lamp is said to take 30 or 60 minutes out of its nominal service life (depending on who you listen to), but once lit and assuming your lamphouse ventilation is OK, it doesn't matter if you then run it for one hour or 1,499. To be honest, I really don't know what a carbon rod costs to buy off the shelf. The rods burn at a given pace and are of a finite length with a maximum limit, a bit like a candle. The important thing is that there are no rods long enough to run a complete feature through one lamphouse, and therefore a carbon arc installation has to be a two projector/changeover setup. When he gave me a tour of the box a couple of years ago, a projectionist at the Tyneside Cinema in Newcastle told me that he could comfortably get 35-40 minutes out of a rod, thereby enabling him to 'double up' reels onto 4,000 foot spools for projection; but that was the limit. So however good the light quality is, you'd never be able to run carbon arcs in a typical multiplex situation.  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 04-01-2004 12:26 AM                     For me, one $668. 3000 watt zenon replaces around $3000 worth of carbons and produce steadier more reliable light without the carcinogenic dust left by carbons. The carbon arc follow spot is now gone too and the booth is cleaner for it. For what is worth, a couple years ago I spoke with a man who ran a single screen (I don't remember where) with a platter and carbon arc, he just pulled the switch, adjusted or replaced the trim and restruck while the film ran. It can be done in about ten seconds.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 04-01-2004 07:31 AM                    As previously mentioned the Futura lamp could get 2+ hrs out of one pair carbons (depending on current of course) but the negative mechanism (screw drive) was only good for about an hour, clamping the new carbon about half way down, then later you'd crank it back down and reclamp by the end. (Positive was continuous via knurled rollers so no problem there.) It would not be that difficult for some ingenious individual, good with metalworking & mechanics, to rework the negative feed with a longer screw to get 2 hrs worth of travel. Then you could definitely do carbon arc & platter.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 04-01-2004 08:09 AM                        When I worked at the Grandview Drive-In, we burned National 11mm x 20 inch (L0109) rotating positives in Ashcraft lamphouses at about 120 amperes. One rod would typically be sufficient for three full 2000-foot reels, somewhere close to 5 inches per reel. Short stubs were used up for showing short reels or cartoons. You definitely never wanted to "cut it too tight" on the positive, lest you flame out or damage the water-cooled silver jaws. Likewise, the 3/8 x 9 inch National "Orotip" copper coated negative (L1124) would be good for about three reels (about 2 inches per reel).  |  IP: Logged Jim Spohn Film Handler Posts: 95 From: Bakersfield, CA, USA Registered: Jan 2003 posted 04-01-2004 09:09 AM                     We run 60 amps on 11mm X 20" rotating positives and it it burns at the rate of 10 minutes per inch. The shortest we can burn down to is about 3".  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 04-01-2004 09:15 AM                        At the Avon, we burn 8mm positives and 7mm negatives at about 65 amps in Enarc lamphouses. A 20-minute reel will burn about 4 1/2 inches of positive and 1 1/2 inches of negative. Since we use 9" negatives and 14" positives, we get about three reels per positive and six per negative. Obviously, this varies, since not all reels are full. I forget what the feed rate is at the Cape Cinema (haven't worked there in a few years), but it's similar. Enarc lamps could probably burn about 40 minutes continuously before needing to re-clamp the carbons.  |  IP: Logged Demetris Thoupis Phenomenal Film Handler Posts: 1240 From: Aradippou, Larnaca, Cyprus Registered: Apr 2001 posted 04-02-2004 12:42 AM                     "Its been many hours and many days That carbon just went awayyyyyyyyyyyyy Because NOTHING COMPARES NOTHING COMPARES to CARBONNNNNNNNNN"  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 04-07-2004 06:21 AM                        There is no reason why carbon arc lamphouses could not have been engineered to burn longer rods so that full features of 2, 2.5 hours or even longer could not be accomodated. It is really just a quirk of history that the xenon technology hit before anyone thought of redesigning the carbon arc system. Once the advantages of xenon became apparant to the exhibitor -- teh adv advantage, btw, had nothing to do with the quality of light on the screen, but everything to do with his ability to run multiple screens using automation and eliminating mulitple projectionists salaries -- it caught on like wildfire. There is nothing that will give an exhibitor a hardon faster than saying he can run 15 screens with a single projectionist instead of 15 projectionists. Before the manufactures of carbons and carbon arc lamphouses could unveil a competing long-play carbon arc system, everyone was running mesmerized to xenon, which, as we all know, never dies before its rated life, never explodes before the reflector's rated life and never, EVER flickers! Has anyone ever done a study (I mean anyone other than xenon manufactures) that compares the light output per watt for carbon vs xenon? I have a 40ft screen that has a beautiful picture -- bright with excellent contrast and burning carbons at 3200w (80Ax40V). According to one of my suppliers, that screen would need a 4000w xenon for the same bright image. If this is true, then over not a very long time xenon could be much more expensive compared to carbon if the extra cost of energy consumption is figured in.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 04-07-2004 08:43 AM                    I'm not sure how wide the cone of light emerging from the positive crater actually is but just in general seeing the relatively shallow mirrors within a carbon lamp vs. the deep reflectors of modern xenon lamps I have to wonder what sort of fantastic light outputs might be possible with a carbon arc lamp designed around a state of the art deep reflector. Perhaps a xenon unit could be adapted or maybe this would have to be specially designed using modern optical CAD techniques. Deep but with a small notched out area directly above the arc flame. 2+ hour operation is not a problem but how well did those automatic positioning systems work? They were pretty crude, no? Imagine what could be done today. You could really have a fully automatic lamp that needs no attention at all over the course of the show. Autostrike, too, of course (probably mechanical but I'd bet a xenon ignitor would work too).  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-07-2004 08:44 AM                     The Morganite AutoArc was designed to bun the 16" copper clad positive and could operate for 2hours unatended and also had an autostrike feature  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 04-07-2004 10:40 AM                     Jim, What lamphouse are you burning 11mm positives at 60 amps? What size negative are you using?  |  IP: Logged John T. Hendrickson, Jr Jedi Master Film Handler Posts: 889 From: Freehold, NJ, USA Registered: Apr 2001 posted 04-07-2004 10:54 AM                     I just spent yesterday afternoon at the Count Basie Theatre in Red Bank, NJ with our tech, Bob Peterson from New England Theatre Service, adjusting the Peerless Magnarcs in preperation for a screening next Monday night. We are putting out fantastic and steady light on the 39 foot screen with those two old gals. Still have some minor adjustments to make on the carbon feed motors, but overall we are ready to roll. Since the Basie only runs film sporadically, it doesn't make sense to convert to Xenon. As long as we can maintain the Magnarcs you will be able to view film by arclight there.  |  IP: Logged

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