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Author Topic: Scope Lens orientation? Andrew Bangs Expert Film Handler Posts: 148 From: Kerrville, Texas, United States Registered: Sep 2008 posted 09-04-2008 12:47 PM                        I have just recently notice that our scope lenses were oriented with the oval shape in the virtical axis. As I am a bit of a nube... Is this correct? My first instinct is that they should be oriented horizontaly. Having said this the picture looks ok with it in the Vertical but I just want to be sure. Sorry I think this is in the wrong thread and should be moved to film handlers. I'll get the hang of this...  |  IP: Logged Jack Theakston Master Film Handler Posts: 411 From: New York, USA Registered: Sep 2007 posted 09-04-2008 12:54 PM                     Vertical oval is correct. Remember, when you're looking into the front, the light is being squeezed at the other end, not expanded.  |  IP: Logged Galen Murphy-Fahlgren Master Film Handler Posts: 405 From: Canton, MI, USA Registered: Oct 2007 posted 09-04-2008 02:54 PM                     You will know immediately if your scope lens is oriented wrong. I had one at my old theater that would creep over slowly, and if that theater had flat movies for a while, the first start with a scope movie could take you by surprise with the image as a narrow diagonal line across the entire front of the auditorium.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 09-04-2008 06:40 PM                     ..and the little numbers on the outside of the barrel means throw focal length from aperture to screen and the barrel is usually locked into place for that correct distance .. which only a tech should change that if needed..  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 09-04-2008 08:44 PM                     And this is in Ground Level why?  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 09-04-2008 08:56 PM                     cuz Andrew, being a noobie, forgot to change forums when he began this thread. As he mentioned above, he's learning.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 09-04-2008 09:52 PM                       Remember, you're looking at a prism. The light is refracted outward (horizontally) when it hits those asymmetrical slopes on the sides. I don't know where you can find one right now, but if you ever look at a cross-sectional drawing of an anamorphic lens, it will be obvious.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 09-04-2008 10:53 PM                     As Galen alluded, if your scope lens isn't turned the right way, the picture won't line up with the screen. Therefore, if your picture fits the screen your lens is in the right way.  |  IP: Logged Andrew Bangs Expert Film Handler Posts: 148 From: Kerrville, Texas, United States Registered: Sep 2008 posted 09-05-2008 12:15 AM                        Cheers Guys I appreciate it. I figured it was right but I didn't know if their was some Jedi Secret trick or not. Monty Thanks for the additional info I was slightly curious about those numbers on the outer ring. Ok since I Think I have your attention I have one more lens question. Actually I guess their are two. First, I have noticed some pictures Keystone but only on one corner (usually upper left or lower left). What causes this? Is it the Lens orientation going out of whack or is the projector its self out of position. Second, I have one screen where no matter what I do I cannot get the outer Edges in focus. The center of the screen is crystal clear but the sides of the screen are a blur. The last guy told me it had been like that forever and to just live with it but that is unacceptable to me. If I adjust the focus it just seems to shift from side to side so right now I have it split even. It is a pain and we get a comment on it once every couple of weeks. Thankfully it is on one of our smaller screens which gets the movies that are on the way out. But if it happens to one of our bigger theaters we will never hear the end of it.  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 09-05-2008 12:45 AM                     quote: Andrew Bangs If I adjust the focus it just seems to shift from side to side so right now I have it split even. Your lens is not on the same plane as the film aperture meaning one side of the lens is closer to the projector than the other. There's no way you'll be able to get overall focus on that without adjusting. What sort of machine are you running?  |  IP: Logged Andrew Bangs Expert Film Handler Posts: 148 From: Kerrville, Texas, United States Registered: Sep 2008 posted 09-05-2008 12:55 AM                        They are Horizon Projectors. it takes two allen set screws to release tension on the lens plus I think their is a Spacer ring. I will check tomorrow if it is seated correctly. I am pretty sure This may also be the incorrect lens for this projector as they told me the old one was dropped so they grabbed a scope lens from our old theatre which used Strong Projectors.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 09-05-2008 02:00 AM                     quote: Andrew Bangs First, I have noticed some pictures Keystone but only on one corner (usually upper left or lower left). What causes this? Is it the Lens orientation going out of whack or is the projector its self out of position. Is the machine center to screen, or off to the right some? If neither, wonder if you have an aperture plate that wasn't cut correctly to compensate keystoning. As long as the scope image is in true vertical-not twisted to either side, I'd call it bad aperture cutting. quote: Andrew Bangs This may also be the incorrect lens for this projector as they told me the old one was dropped so they grabbed a scope lens from our old theatre which used Strong Projectors. Then, wonder if they'd even check the focal length of the prime lens between the one that the Horizon used, and the one that the Strong used. Also, if that one that was on a Strong was dropped, 10 to 1 that the lenses inside that attachment got jolted some and has thrown the whole lens elements inside out of kilter. ... why you do take special attention and being careful with anamporphic attachments. -Monte  |  IP: Logged Andrew Bangs Expert Film Handler Posts: 148 From: Kerrville, Texas, United States Registered: Sep 2008 posted 09-05-2008 02:21 AM                        The aperture on the Horizons Change Automatically with the rotation of the lens turret will Try to get you a pic But it is still possible that the aperture is miss alligned or cut wrong. My bet however is that the projector is not flat to the screen I just thought that would keystone the Whole Side not just the top or bottom corner. Perhaps their is a combination. Thanks for the Ideas of where to look.  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 09-05-2008 08:39 AM                     The ideal projection angle would be perpendicular to the center point of the screen with the projector set absolutely level (0 degree rake). Keystone is a function of projection angle and rake, and will vary accordingly. Properly cut aperture plates will [square the image and give the impression that] keystone [has been eliminated]. (Thanks Brad) In some theaters with excessive rake the screen was slanted back to help compensate. [ 09-06-2008, 08:38 AM: Message edited by: Rick Raskin ]  |  IP: Logged Andrew Bangs Expert Film Handler Posts: 148 From: Kerrville, Texas, United States Registered: Sep 2008 posted 09-05-2008 08:30 PM                        I just found out today that the Screens in our theatre were suposed to be Tilted 7° but unfortunately that never happened so we will always have some keystone. I did futs with The lens that was going blurry on the sides and after removing it and checking he spacer mount I heard a faint little pop. Either it's fixed or I broke the lens... Good news is it's Fixed. Thanks for tip on that one John.  |  IP: Logged

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