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This topic comprises 3 pages: 1 2 3
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Author
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Topic: Light on Screens (DRIVE-In)
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Monte L Fullmer
Film God
Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004
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posted 05-28-2008 12:19 PM
quote:
I like the footstool to be able to get up high enough to do the tread work!
I just use the stool to hit the upper roller, then I can thread up the machine standing on the floor.
With threading where the machine is rather higher than me since I thread standing on the floor, I put black spots on the frameboss of the machine with a marker so I can match up framelines that way without having to use the framebox.
I have a spot down on the INT assembly underneath the trap to line up a frameline and a matching arrow on the dowser cover with it's corresonding spot on the assembly for assembly frame center.
Doing this, I can thread in frame every time.
No, the lady that owns this drive-in isn't too afraid to spend money, just that the expenditures to get more light out - to get this Century to handle a larger bulb with a watercel and a larger lamphouse/rectifier assembly, just isn't in her budget right now.
Place only operates a few months of the year and only on wknds. And last year wasn't a good year with a lot of the junk that came out. This year, as soon as the hot movies drop to discount levels (she runs discount films out there), then she'll get some serious business.
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Monte L Fullmer
Film God
Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004
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posted 05-28-2008 03:54 PM
quote: Ron Funderburg
There are far too few drive-ins around
THX for the comment! ![[thumbsup]](graemlins/thumbsup.gif) Sadly, there were scads of DrIns in this area, but all were knocked down for businesses.
(in 1969, I started at this Drive-In and began my crazy association with this industry here.Interestingly enough, this Drive-In is still in operation.)
From the good dozen in this area at one time, now there are only two standing - the one I work at, and the one close to the Ida/Ore border, which the latter is in prime/mint condition and really draws the crowds in the three days it's opened. That small 250 car yard is always full during the summer.
I also do service work for both Drive-Ins. The other one has a water cooled XL/4star setup mounted in front of a CFS4500 console, 4200w bulb inside, with an AW3 for their film transport.
Luckilly, her scope pictures looks pretty good - thank goodness for full open apertures...lol
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 05-29-2008 10:12 AM
Yeah, I want to see that 21" lens. Presumming no lens barrel and just magically suspended glass, a 4" OD lens would effectively be stopped down to f/5.5. For a standard 70.6 OD barrel, you are pretty close to f/8.
I presume this thing flares out oat the end to get "some" light out of it.
As to light...I've done a fair amount of experimenting with it, myself.
The lamp, reflector, shutter, and Lens ALL play into the light the system puts out.
The shutter is easiest to conceptualize. The more opening it has, the more light, as a percentage it will let through. Most mechanial shutters have an effective 50% efficientcy. Simplex is closer to 53% if you tweek it just right but is safer at 50%. Kinoton also is better than 50%. The current Kinoton FP30E Premiere, at 57% efficient will increase your light about 14% over a typical projector, all else being equal
As for the light itself, different lamps work better/worse with different reflectors. It isn't just about creating the lumens at the arc but how the reflector collects that light and focuses it to the lens. It is also about how the reflector mates with the lens to efficiently get as much light as possible though the lens.
I have tested 5K lamps that, in the same lamphouse, same lens put out 8% LESS light than the 4K lamp, both running at their respective powers!
I have also tested 4200-watt lamps that will put out 20% more light than their 4KW counter parts. Or the absolute kicker...a 4500 watt lamp that put out nearly 40% more light than the 4KW counterpart!! All without changing anything but the lamp.
I'm also finding that the evenness of the illumination, not just the center, varies based on reflector/lens characteristics.
I have no doubt that Technolite has specific lamps they have you use with their optics and they would also be wise to specify lenses too as they do play into it.
The bulk of my testing has been with Kinoton projectors/lamps with ISCO and Schneider lenses. These results may not apply to other combinations.
The 4200-watt lamp in question was ASL's XM4202. The 4500-watt lamp is still under test.
The 4KW lamp (reference used for all of the above) was Christie's CXL-40SC.
The 5KWs were Christie's CXL-50SC AND the ASL XM5000HS...both dogged. I suspect the arc was too big and or the anode was too large for efficient light transmission though a 1.85 aperture.
Steve
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