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Topic: 7000 Watt Lamphouse for DI, good idea?

Justin West
Master Film Handler

Posts: 271
From: Peoria, IL, USA
Registered: Jul 2001

posted 01-23-2005 02:36 PM

While I am still new to the concept of f-stop and proper lenses, I appreciate the theoretical vs. street-wise discussion going on...as well as the advice, from all. I have started looking at some old 4" lenses...Kollmorgens, as a matter of fact, but of the two that had potential for my needs, one had a star-shaped burnmark about 3/4 of the radius from the center and the other one had tons of bubble or water droplets situated as if between layers of the lens(es).

Mark: would you elaborate a little on this "cementing" issue with such lenses? Thanks agin! [Roll Eyes]

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 01-23-2005 02:44 PM

Justin,
The cement used in those older lenses was basically a highly pure derivitave made from balsam sap. Its just called Balsam by potical techs and is easily burned in those older lenses with high temperatures that large arcs and xenons can put out. Ususally its the rear group or the second group in from the rear that this happens to. That star you mentioned is actually the Balsam crazing from heat and stress, its melted and the elements have pulled apart due to heat expansion and stress!

Not to worry though as we can have those cement problems repaired and today the elements are re-cemented with more modern U-V cured adhesives that will not be affected by heat. These newer adhesives are also much more optically transparent than the Balsam that was used back then. Even anamorphics with burned cement or crazed elements can be repaired! We are fortunate to have access to a local retired Air Force optical tech that does this sort of work today for a living and he does all of our older lens repairs. I have re-cemented lenses myself while at Canon USA but CLACO does not have a "Clean Room" atmosphere to allow us to do it in house.
Mark @ CLACO

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Richard Greco
Phenomenal Film Handler

Posts: 1180
From: Plant City, FL
Registered: Nov 2003

posted 01-23-2005 06:51 PM

Hey Justin, FYI

There is a 4th screen going up at my DI, sigh..... There are many things I have to say about that, but getting rid of a 55 year old marquee really stinks in my humble opinion.

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Richard Greco
Phenomenal Film Handler

Posts: 1180
From: Plant City, FL
Registered: Nov 2003

posted 01-24-2005 11:08 PM

Ok, I just read on one of my new flat lenses, "F 1.9" What does this number mean?

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 01-25-2005 11:00 AM

It's the aperture or f-number. Essentially it is calculated by dividing the focal length of the lens by the effective diameter of the aperture. For example, if you have a 100mm focal length lens and an effective aperture diameter of 50mm, you have an f/2.0 lens. If you reduce the effective aperture diameter to 25mm, the lens is f/4.0.

The lower the f-number (larger the aperture diameter), the more light the lens can transmit, and the less "depth of focus" the lens has.

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Justin West
Master Film Handler

Posts: 271
From: Peoria, IL, USA
Registered: Jul 2001

posted 01-25-2005 11:56 PM

quote: Richard Greco
Hey Justin, FYI

There is a 4th screen going up at my DI, sigh..... There are many things I have to say about that, but getting rid of a 55 year old marquee really stinks in my humble opinion.

Awww, that is a disappointment...it's a nice marquee, nothing extravagant but a nice neon marquee...they're not going to tear it down are they Richard? Surely they would disassemble it from the structure, for re-use down the road or repositioning elsewhere??? I hope it would not be replaced by some plastic faced sign with fluorescent tubes behind...UGH! [Mad]

BTW, Mark: Thanks for the cementing lenses info...could you advise on the lens that had tiny bubbles or water droplets sandwiched within? Is a lens in this condition usable? What possibly led to this condition? thanks.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 01-26-2005 12:04 AM

quote: Justin West
BTW, Mark: Thanks for the cementing lenses info...could you advise on the lens that had tiny bubbles or water droplets sandwiched within? Is a lens in this condition usable? What possibly led to this condition? thanks.

Could be two things......

1. Elements just at the beginning of seperating fomr excess heat.

2. Could be air bubbles trapped in the glass during manufacture. These generally will not afffect lens performance unles there are alot of them or several large ones.

Again, seperated elements are generally a piece of cake to repair, they are one of the easiest repairs to do involving working on actual cemented groups.

Hope this helps....

Mark

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Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

posted 02-03-2005 11:08 AM

quote: Steve Guttag
I don't tend to guess at the outcome of a projection systems I set up.

*YAWN*

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Laurence Hammett
Film Handler

Posts: 16
From: Los Angeles, CA, USA
Registered: Feb 2002

posted 02-09-2005 07:52 PM

I have just finished the Largest all-Technolight installation on the Planet. The Mission Drive-In - Montclair California. We dumped the 4 Christie Lamps from their consoles in favor of Kneisly Zenex's which have been retrofitted with the Technolight system. The Inventor, Robert Miniachi came down and we did this and one screen at the South Bay DI in Chula Vista.

The Company had hired me because I had "improved" the light from the Christies to 1.1 FL. What a Joke. We are getting in excess of 5 in ALL screens regardless of size and throw. But more than that the colors and definition are exquisite! Something you won't find in a metal reflector at least for very long.

This is a SYSTEM Just like THX is a system. Just as THX isn't just the booth Crossover. Technolight is not just the reflector.

Contrary to popular belief they ARE NOT kinoton reflectors. They are Designed By Robert and matched to the throw, the lenses and picture sizes. Aligned to within an inch of their lives, Biggest shutter opening possible without ghosting. and a bulb Robert designed and made by OSRAM. The LTI is a knock-off of this bulb and runs hotter and is not as bright. I know as I tested one at South bay. With the LTI I got 5 Fl and with the OSRAM I got 5.5.

When you look at these screens it is like going to a walk-in.

These are 4200 watt bulbs running at 145 amps.

Technolight makes kits for most any lamphouse even the Christies we replaced but Robert really likes the Zenex for Drive-ins. The Rear bulb holder is stable and The Mirror moves. Neither of those gets adjusted at bulb change. Just the focus.

When you take into account the long throws and big pictures this is truly a new age in light. Combined with FM Stereo it is safe to come back to the Drive-In!

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 02-09-2005 09:23 PM

quote: Laurence Hammett
When you look at these screens it is like going to a walk-in.

What is this... some sort of Joke? FYI, Walk-ins typically run at 16 foot lamberts or a tad more...... Your 5.5 foot lamberts is just a tad bit shy of that 16fl mark SIR..... Also don't forget to let everyone know about the incredibly SHORT lamp life, and good luck getting that early failed Osram credited under warranty! Also, which Xenex's are they and what projectors?

Mark @ CLACO

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Laurence Hammett
Film Handler

Posts: 16
From: Los Angeles, CA, USA
Registered: Feb 2002

posted 02-09-2005 09:36 PM

If you were to get 16fl in a drive-in it would be washed out and you would see the slats in the screen. I will leave it to other more brilliant people in this forum to explain why just looking at fl is a mistake. It has something to do with light per square foot of screen area. The bigger the screen the less total footlamberts necessary to achieve optimum light. Also the definition is different because of the increased photons hitting the screen.
I didn't pay attention to what model Zenex's. The projectors are standard simplex xl's

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 02-09-2005 09:42 PM

You've been brainwashed by someone(north of the border) thats for sure! I left a customer in North Central Indiana with close to 14 fl on his 50 foot D.I. screens several years ago(running just 3kw). The images were terriffic! No visible slats either.... a well maintained screen also makes a huge difference...

Mark @ CLACO

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Richard Fowler
Film God

Posts: 2392
From: Ft. Lauderdale, FL, USA
Registered: Jun 2001

posted 02-10-2005 09:01 AM

The Kneisley Xenex I lamphouse uses a glass reflector and still is made as a production item. The existing reflector does work great for medium and long throw situations based of the F- speed of their reflector. The man in Canada has several "custom" reflectors? I could see the expense of having one glass blank mold made but several? He may have one and speced the balance from the glass reflector companies in Europe and Asia. 16 foot lamberts will wash out [Roll Eyes]

most prints are timed for 12 - 16 and it is indeed rare that timed thin prints for drive-ins are readily available. The large image being acceptable at a lower light output if this image surrounds your field of view, such as IMAX but in a drive in situation...outside of the first row, your eyeballs will not be overwhelmed. [Razz]

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 02-10-2005 02:31 PM

SMPTE Recommended Practice RP12, "Screen Luminance for Drive-In Theaters" specifies:

quote:
4 Luminance level
4.1 In an ideal situation, when permitted by the
technology of motion-picture projection, and when
the viewing environment is sufficiently close to
that of the indoor theater, the screen luminance
and distribution shall be that specified in
ANSI/SMPTE 196M, 16 fL ± 2 fL (55 cd/m2 ± 7
cd/m2), as measured from a position on the
longitudinal centerline of the ramp area and midway
between the foremost and rearmost ramps.
4.2 The recommended minimum luminance at
the center of the screen shall be 7 fL (24 cd/m2),
as measured from the central position defined in
4.1.
4.3 When maximum compromise must be made,
as discussed in annexes A.1 and A.2, the luminance
at the center of the screen, measured
from any car position, shall in no case be less
than 4.5 fL (15 cd/m2).

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 02-10-2005 07:37 PM

Thanks John for posting that SMPTE spec!! Indeed there are large tradeoffs in using Roberts design. While it does give you more light there are hidden added expenses in lamps that he generally fails to mention.

I was able to get the 14 fl in Indiana with the use of High Speed movments in the X-L's. This customer also paints and maintains his screens every two years, few go to this extent. The HS movement raises the projector to nearly 70% light efficiency and also provides a seemingly sharper image than a standard movement.... everyone I know thats seen film projected by them agrees things are sharper.

Mark @ CLACO

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