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Author Topic: Drive-In Construction Ken Russell Film Handler Posts: 23 From: Smyrna, GA USA Registered: Jun 2004 posted 07-10-2004 01:48 PM                     Hi all. I have seen a lot about the longest possible throw in this thread. I too am toying with the concept of a new drive-in. I would pose this question... If I wanted screens 75 to 80 foot wide (for scope) what would be the shortest throw I could have given off the shelf lenses? Now, add to that the concept of rear-projection. What material could be used for the screen? I have found that the normal indoor vinyl material is only good down to 40 degrees F. My initial thought was mylar (good for something like -40 to 300 degrees). Does anyone have any experience with the loss (or possibly gain) involved in rear-projection with different screen materials? I have a lot more to consider and seek help on but will leave it at this for now. Will gladly take this to another thread if appropriate. Ken  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 07-10-2004 02:31 PM                     For calculation of projection geometry, use the Schneider Lens Calculator. You can use a variable prime or Magnacom to further adjust the image size beyond the standard lens capability (subject to the loss of light and contrast). For rear projection, you're going to need a screen specifically designed for that purpose. Vinyl, etc. isn't going to work because it's opaque. The effectiveness of rear projection in an outdoor setting is questionable at best. Ambient light from behind the screen is going to kill your ability to accomplish this, unless you're planning on enclosing the area between the projector and the screen.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 07-10-2004 07:56 PM                    Forget about rear projection at a drive-in. What have you guys been smoking? Besides the usual problems created by RP such has hot spots, the huge wasted space behind the screen, and, in an outdoor setting, the ambient light issue, how could you create a screen which will resist the enormous wind loads a DI screen must withstand yet have NO supporting frame members crossing behind it?  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 07-10-2004 11:06 PM                       quote: Ken Russell If I wanted screens 75 to 80 foot wide (for scope) what would be the shortest throw I could have Seems like I wrote about this somewhere and had a formula worked out for laying out the field, taking into consideration maximum throws with f/2.0 lenses. Maybe it was here on Film-Tech, but... It could've been here. Check it out. Drive-In Workshop  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 07-11-2004 08:16 AM                        Really short focal length lenses will have more issues with "focus flutter" due to their shallow depth of focus, especially with the high power levels needed for large drive-in screens. Keep the throw long enough to use at least a 50mm lens for 1.85:1 "flat".  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 07-11-2004 11:00 AM                       John, don't you mean depth of field? My ramp formula also put the lens choices right in the middle of the "comfort zone" of available focal lengths, so you'd have some room to compensate for extenuating circumstances. Wish I could remember where I wrote that...  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 07-11-2004 01:10 PM                        "Depth of Field": what is in focus when using a camera. Increases with shorter focal length lenses. "Depth of Focus": what is in focus when projecting an image. Decreases with shorter focal length lenses. [ 07-11-2004, 02:18 PM: Message edited by: John Pytlak ]  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 07-11-2004 01:51 PM                       I've never heard "depth of focus" used before. At least, I don't think I have. I may have used it myself, though. Hell, I don't know. I've been out of this game too long.  |  IP: Logged Ken Layton Phenomenal Film Handler Posts: 1452 From: Olympia, Wash. USA Registered: Sep 1999 posted 07-11-2004 06:41 PM                     Rear projection at a drivein would not work because of the need to brace the screen not to mention the fact the plastic materials that makeup a rear screen would fly right off in a windstorm. And don't forget about how the ultraviolet rays of the sun deteriorate/yellow plastics and insects/birds would eat it.  |  IP: Logged Ken Russell Film Handler Posts: 23 From: Smyrna, GA USA Registered: Jun 2004 posted 07-12-2004 08:21 PM                     Hi again. I understand the issues presented here. Tim, I find your pub on the drive-in workshop invaluable. John, your recommendation of a 50mm minimum on the lens a welcomed starting point. Adam, thanks for the lens calculator. The one I had was failing. Now, with respect to Barry's issue as well as mine, please allow me to throw out my issues and desires. 1 - I desire a family entertainment complex with daylight uses as well as movie presentation. 2 - I understand that multiple screens is desirable to be able to run multiple first run films. 3 - I see the need to have a screen running an "R" feature not to be visible from the field of one running a "PG". 4 - I feel that as much as possible concession and projection facilities need to be consolidated for cost reduction and reliability. 5 - I see the need to keep duplicated equipment (projectors and such) to a minimal number models so that spare parts can be kept to a minimum. 6 - The most efficient use of the land needs to be used. My thought is 8 screens with the the fields laid out around the screens like the spokes of a wheel. Each field would be of a traditional form with about a 45 degree spread. My approach of rear-projection is to consolidate the facilities under the screens. So, how can I attack and conquer the impossible here? Equally to the point, can any of this apply to Barry's situation? With the 50mm guide a cluster of screens in a octagon form with each side being about 85 foot and a screen area of about 70 foot wide projected from 10 foot off the center comes close. The projector can be raised to a level that is exactly perpendicular to the screen to allow for the greatest image efficiency. On the issue of UV toleration I know that Mylar can stand up to it where the purpos produced screen material can not. Does anyone know of another option? Same thing with temperature (cold) tolerance. The "Hot Spot" issue mentioned by Steve I don't have real answers for. The screen material will make a difference and intentionally offsetting the projection would induce other issues. Help. Wind loading... Well Mylar has the lateral stability not found in other materials but 2400 sq ft of sail is still a bit much. What if a matrix of thin aircraft cable were placed behind it? Viewed from 75 foot plus would they even be visible? Anyway, Help. I do see the need to box the throws to stop ambient light. I think this could be soft material but welcome other suggestions. Forgive me if I seem to be flogging a dead horse but I have to believe that just because it isn't or hasn’t been done doesn't mean it can't be done.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 07-12-2004 09:11 PM                    I hope land is cheap where you plan to do this. Let's see a 70' width screen...and presuming that's Scope and that you are doing common height projection that gives you a 1.85 picture of about 56'. Using John's rule of thumb of going no shorter than 50mm you will need to have the projector about 133' back. And the projector on the opposite side of the booth needs to be 133' back from the opposite screen. (167' if you want to fill 70' @ 1.85) So your customers will need to walk not only the length of the car park area but half a football field beyond the screen to get to your central facilities. Which of course cannot have any illumination which will get up onto the screens. Remind me again what advantages you hope to gain even if the problems were solvable. It can't be the central facilities...that can and is already done with projecting outward to distant screen towers.  |  IP: Logged Dave Bird Jedi Master Film Handler Posts: 777 From: Perth, Ontario, Canada Registered: Jun 2000 posted 07-15-2004 07:56 AM                        A rear projection drive-in was apparently tried - and FAILED - at the "5" in Oakville Ont. It was quickly converted to traditional. I've no idea why they tried it, it was a single at the time. The HUGE 100 ft+ long building now has two screens (one where the original was and one on the side). A central screen structure for 8 screens would be WAY bigger than you need, consolidate your concessions and projection, but fan your screens out.......  |  IP: Logged Barry Floyd Phenomenal Film Handler Posts: 1079 From: Lebanon, Tennessee, USA Registered: Mar 2000 posted 07-15-2004 03:13 PM                        The last time I posted to this thread, I wanted to start a drive-in. Now... several years later, I actually built one. I can honestly say that our traditional Selby screen tower was one of the lesser expensive items we built. A little under $44k.. but well worth it. Tuesday night of this week we had 70 mile an hour straight-line winds blow thru the drive-in. We lost power, lost some fence panels, trash cans blew across the field like empty Coke cans, and our 8 yard dumpster was shifted off the concrete pad, but our screen stayed put. No damage at all. While the idea of rear projection screens seems novel... from a business perspective, I can't see why you'd want to? You don't really gain anything. What we actually built looks almost identical to the first picture I posted on the first page of this thread. We didn't do the "Diner" thing... instead focussd all of our attention on the theatre aspect of the development. Here's a link to the "Construction Photos" of our theatre. I don't claim to be a "drive-in expert", but this is what we did.  |  IP: Logged

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