Film-Tech Forum ARCHIVE: Brightest Outdoor Screen I've Seen

This is topic Brightest Outdoor Screen I've Seen in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Dave Bird (Member # 490) on 07-08-2000, 08:29 AM:

I don't know if this warrants discussion, but my wife and I agree that last night we saw the brightest drive-in screen we've ever seen. Not only that, it's as bright as any MOVIE I've seen. Was it that Chicken Run and Gladiator are bright prints? We were a little concerned, this screen faces the sunset, but presentation was just excellent. About a 200-230 foot throw to at least a 60-70 foot screen. On visiting the booth, I saw a Century projector lit with a Kneisley-conversion of an old Peerless Magnarc at ONLY 2000W! What a magic combination though, I put it ahead of theatres I know are running 3 and 4K. Have any of you experienced this? A place that just seems to click? To Tim Reed, I believe this theatre is what you speak of, the drive-in of the "future". Old single, converted to twin, short throw, and this is unique, the rows are spaced 30-33 feet instead of the usual 40. 200 spaces within 300 feet of the bright screen. Gets everyone close. Marvelous! Back screen is a little further, he uses 3K and says it's brighter still, but it's a bigger screen protected from sun.

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Dave Bird

Posted by Gordon McLeod (Member # 33) on 07-08-2000, 11:32 AM:

What drive in was it
the peerless cobversion usually produced lots of light
If it was the lindsay drivein it is a 40' screen on the original the newer one has 60' with a 3k xenex2
To see a bright one also check out the north york drivein

Posted by Ken Layton (Member # 133) on 07-08-2000, 11:38 AM:

The Rodeo drivein in Port Orchard, Wash. has got a really bright picture on all 3 of their screens. Their picture is brighter than most indoor theaters! They run Strong X-60-C's with Brenkert projectors.

Posted by Tim Reed (Member # 137) on 07-08-2000, 02:11 PM:

Dave, that's the combination alright! Fast optical trains and low-density prints are things of the past, so the only way to guarantee bright pictures is to not go overboard on dimensions. It's as simple as that.

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Better Projection Pays!

Posted by Dave Bird (Member # 490) on 07-08-2000, 04:15 PM:

Yes Gordon, Lindsay Twin. I know you would know (cuz I think you probably equipped this place), but damn, I almost cannot believe that screen 1 is only 40 feet, picture is SO good, but since it's you, I believe it! As I said, this place is sort of "scrunched" together, but it works very well, getting everyone closer. Not sure how far 1st row is from screen, closer than usual though. They are able, I think, to have rows so close because the screen is quite high. I don't know if you worked on Kingston as well, but the 48 footer there always looks better than the 120' (?) original.
(Screens are measured horizontally, aren't they?)

Posted by Tim Reed (Member # 137) on 07-09-2000, 08:30 AM:

Dave, it may be important to note that you perceived the screen as being larger than it actually was.

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Better Projection Pays!

Posted by John Pytlak (Member # 331) on 07-10-2000, 06:52 AM:

Achieving the SMPTE aim of 16 footlamberts on a 40 x 17 foot matte white scope screen should be possible with about 3000 watts. They are obviously doing a good job with what they have (efficient optics, good alignment, clean screen).

BTW, never trust your eyes alone when measuring screen luminance. A screen luminance meter is needed for accurate readings. A picture projected at 10 footlamberts can look "bright" in a drive-in, but 16 footlamberts will look even better.

For more information on measuring screen luminance, see:
http://www.kodak.com/US/en/motion/newsletters/reel/spring98/pointers.shtml
http://www.kodak.com/US/en/motion/newsletters/notes/march2000/pytlak.shtml
http://www.kodak.com/US/en/motion/newsletters/notes/june2000/pytlak.shtml

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

Posted by Gordon McLeod (Member # 33) on 07-10-2000, 09:41 AM:

When I installed both those systems many years ago ( about 87) they had 14.5 fl in the centre on each of there screens and 12 in the corners
Haven't been back since

Posted by Dave Bird (Member # 490) on 07-10-2000, 10:44 AM:

Fascinating, John, to read the articles on how many first-run theatres fall so short on luminance. I really thought maybe I was nuts to think that the brightest picture I'd ever seen was actually outdoors (of course, so's the dimmest). Interesting also, Gordon, that you remember the actual readings. Do you remember how far the throws were? I believe Larry (the owner of this theatre) mentioned that he's bought some new bulbs. And though the screens look better than most, he will be painting them for next season. Does anyone still paint outdoor screens for any gain, or is matte the norm?

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Dave Bird

Posted by John Pytlak (Member # 331) on 07-10-2000, 11:34 AM:

Dave:

Remember, it's the SCREEN AREA and GAIN that affect screen luminance with a given projector, lamp, and lens, not the THROW.

Getting a gain surface on a painted outdoor screen is tricky to do consistently. It would ideally take a "pearlescent" paint, sprayed on. A gain screen should be properly curved. When the screen is wet with rain or dew, all bets are off.

I recall the MP Technology Council sponsored some work on gain and directional (i.e., "containment") drive-in screens many years ago, but only a few were built.

Posted by Dave Bird (Member # 490) on 07-10-2000, 02:15 PM:

Ah, the legendary "containment" screen. Now there's a Quixotic quest, to find remnants of any of those attempts. I remember laughing at Tim Reed's response to someone who asked what kind of light source needed to project in daylight - one that's brighter than the sun! I think I also read once about a particular drive-in (the Ford-Wyoming in Detroit I think - still open) where they were throwing one screen some 1600-1800 feet ACROSS a four lane boulevard!
Anyone hear of that?

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Dave Bird

Posted by Sean Weitzel (Member # 244) on 07-10-2000, 08:23 PM:

Maybe the century was equipped with a high speed pulldown and a shorter shutter in order to get more light on the screen.

Posted by Tim Reed (Member # 137) on 07-10-2000, 11:45 PM:

>>Remember, it's the SCREEN AREA and GAIN that affect screen luminance with a given projector, lamp, and lens, not the THROW.<<

I think what Dave was referring to is the discussions we had on the drive-in list, where there were people wanting ridiculous throws. These would get into very slow, long lenses, where light would be lost.

And since Schneider no longer makes anything faster than f/2.0, any new d/i construction will be limited in throw, if they're going to stay with an efficient lens.

Dave, I remember that question! I've never heard of that theatre, though. The longest throw I knew of was at the New Albany d/i, in New Albany, Indiana... just over the river from Louisville. It only had a measly 1,100 ft. throw, and custom lenses. I think the focal length of the flat lens was something like 11 inches!

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Better Projection Pays!

Posted by Dave Bird (Member # 490) on 07-11-2000, 07:21 AM:

There's something I need to learn more about,
optics. Where would I look to learn more about what an "f/2.0" is and possibly a formula or chart which tells me what size screen/bulb/lens gets me how many lamberts?
Thanks again.

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Dave Bird

Posted by John Pytlak (Member # 331) on 07-11-2000, 10:56 AM:

It's not quite that simple, as there are many factors that affect the efficiency of a projection system in putting light on the screen. Obviously lens f/number, shutter angle, number of shutter blades, lamp size, screen gain, etc. affect screen luminance. But the f/number of the lamphouse system, type of reflector, alignment, type of port glass, etc. also can affect efficiency.

A good guide is the Strong International "Lens Selector and Picture Size Comparator" slide rule, which is based on "typical" installations.

Posted by Tim Reed (Member # 137) on 07-11-2000, 11:55 AM:

I use Schneider's Theatre Design Pro software (available free on their website). You can change any variable (screen width/height, projection throw, focal length) and watch everything else follow. A list of suggested Schneider lenses appears in the window, for a given combination of variables, if available. I watch the f/#'s of the displayed lenses, to find the upper limits. This gives a good idea of what can and can't be done with what's available.

Since a previous query on this forum indicated that currently-available lamphouses are at least f/2.0, the lenses are the element that's most likely to become a bottleneck, if not selected wisely (given proper optical alignment and components, of course).

The f-number is a mathematical statement, relating to the angle of light that a given component will pass. Just like in an SLR camera.. the higher the f-number, the smaller the aperture; the slower the lens, i.e.- less light will pass. However, with slower lenses comes greater depth of field and vice-versa. With very fast projection lenses (on the order of f/1.6 or less), it can be difficult to keep a projected image in focus.

The best way to illustrate the importance of matching the various elements in an optical train, is to think about looking down the centers of several, identical donuts, stacked one on top of the other. Now place a donut with a smaller hole anywhere in stack, and you will only see the small opening. This is how a mismatch can limit the performance of the whole system.

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Better Projection Pays!

Posted by John Walsh (Member # 168) on 07-11-2000, 03:41 PM:

Tim, that is not exactly right. Doughnuts with large openings do not affect my ability to focus in on them. I can see them clearly, right down to the little sprinkles. It is true, though, that small openings are preferred since larger aperture openings = less doughnut.

I notice I am now a "Jedi Master." That means I have annoyed all of you with 500 posts. I apologize!

Posted by Dave Bird (Member # 490) on 07-11-2000, 07:05 PM:

I sell doughnuts (among other things)! Holy crap, I better slow down my postings, lest I become a "Jedi Master" before I've even projected any film! Is there any way to disable that Brad

? Thanks Tim, I shall look at the Schneider site. My lenses are B&L.

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Dave Bird

Posted by Tim Reed (Member # 137) on 07-12-2000, 08:47 AM:

John... You are CORRECT, oh great one! I yield to the master. (I like Krispy Kremes the best!)

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Better Donuts Pay!

Posted by Dave Bird (Member # 490) on 07-12-2000, 08:24 PM:

Tim, that software is cool! I wish I knew more about the lenses, I never know which to pick. Also, I wish there were a little program somewhere telling you (roughly) what size bulb on what size screen etc. for how many lumens. Gordon, since you were there for the refurb of the Lindsay DI, do you recall who built screen 2? It looks somewhat like a Selby, but I'm assuming it was built up here.

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Dave Bird

Posted by Tim Reed (Member # 137) on 07-13-2000, 07:33 AM:

The lens given at the top of the list is the best recommended choice for those particular set of circumstances. They get progressively less desireable as you go down the list. But remember, the higher the f/#'s get, the more light you're going to be choking off.

I forget the screen width/recommended bulb size rules of thumb, but I wouldn't chance 2kW past 35-40 ft wide in a drive-in. And 3kW should only be good for drive-in screens up to about 48-50 ft. Any wider than that, and count on going with 4kW.

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Better Projection Pays!

Posted by John Walsh (Member # 168) on 07-13-2000, 09:06 AM:

As JP said, there are many factors that affect screen brightness.

I will just add that a very rough rule-of-thumb was to take the height of the screen squared times 12 to find suggested wattage.

15 foot high screen

(15x15) x 12 = 2700 watts

In actual practice, I find this to give wattages that are a little low, especially with focal lengths below 80mm or so. Remember, though, it's not a formula for actually buying equipment by.

Tim, apparently, Better Donuts (do) Pay! Look at their stock: http://quote.yahoo.com/q?s=KREM&d=t

Posted by John Pytlak (Member # 331) on 07-13-2000, 02:53 PM:

John:

Your "rule of thumb" pretty much agrees with mine of "5 watts per square foot of scope format screen area":

15 ft high x 36 ft wide = 540 square feet

540 square feet x 5 watts = 2700 watts

This "rule of thumb" is based on the Strong slide rule, and assumes a two blade 90-degree shutter, normal (f/2.0?) lens, matte screen with gain = 1.0, and normal efficiency. A properly curved gain screen requires less power, depending on the gain.

Glad our thumbs are the same size.

Posted by Tim Reed (Member # 137) on 07-13-2000, 04:49 PM:

JW: HAAAAAAAAAAAAAAAAAAAAAAAHAHAHAHAHA!!!

JP: So, this Strong sliderule isn't just a lens computer? That's pretty good about the 5 watts... I'm going to have to remember that.

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Better Projection Pays!

Posted by John Walsh (Member # 168) on 07-14-2000, 09:45 AM:

OK, here's a question: Do lens and equipment manufacturers give all the information required to actually be able to figure out screen brightness to within (say) 5%?

I checked a few manufacturer's web site, but did not see "projector efficiency" or "speed of lamphouse," or other numbers that would be required.

Could we create one "master" formula?

Posted by John Pytlak (Member # 331) on 07-14-2000, 10:17 AM:

There have been attempts to "standardize" measurement of light output. SMPTE Recommended Practice RP153 describes a "Method for Measuring 35- and 70-mm Shutter Efficiency", and there was some attempt to specify a measure of total lumen output. Unfortunately, few manufacturers publish "system" performance, since there are so many variables over which they have little control (e.g., the match between a particular lamphouse and lens).

The "rules of thumb" or tools like the Strong "Lens Selector and Picture Size Computer" slide rule are good starting points. I usually err on the side of specifying the next lamp size up, because it's easier to defocus the lamp and get better uniformity, than to struggle to get 16 footlamberts with an undersized lamp.

Working with an equipment dealer, the design specifications should state that the system will consistently deliver 16 footlamberts. They can then work with you to achieve it on reasonable sized screens. (For a 30 x 72 foot screen, don't expect to meet SMPTE standard with 35mm prints).

Posted by John T. Mellor (Member # 468) on 08-12-2000, 01:17 PM:

At the Bucks Drive in that I had to close last year [I didn't own the land just the theatre] it was a single twined down the middle with remote booths in each field 235 ft to the screen 40 x 80 screens simplex XL,s Knisley series 1 with Osram 4k bulbs at 150 amps we were able to get 15 at the middle and 14.2 at the sides lenses were 1.9 fs The big key was to keep everything clean and in alignment also we ran without port glass except when it raine