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Author Topic: How can it be out of focus only on one side of the screen? Tim Turner Film Handler Posts: 87 From: Chula Vista, CA, USA Registered: Jan 2002 posted 01-06-2003 03:33 PM                     Recently a projector started having a problem of projecting an image that is a little out of focus on the left hand side of the screen only. The right hand side of the screen looks fine. I've tried cleaning the lenses and port window but nothing helps. A customer mentioned who is a former theater manager said that we needed to check our "tracking". But we don't know what that means. Does anyone have any ideas on the cause of this problem?  |  IP: Logged Michael Brown Phenomenal Film Handler Posts: 1522 From: Bradford, England Registered: May 2001 posted 01-06-2003 04:00 PM                     ?? Make sure that the gate is clean.  |  IP: Logged Tim Turner Film Handler Posts: 87 From: Chula Vista, CA, USA Registered: Jan 2002 posted 01-06-2003 04:02 PM                     Yes, we've checked the gate everything is clean.  |  IP: Logged Giorgio Volpi Film Handler Posts: 51 From: Caracas - Venezuela Registered: Mar 2002 posted 01-06-2003 04:09 PM                     Tim, what projector are you using? The problem is for all formats or only one? Check the lens, it could be damaged. Check the window glass. Giorgio.  |  IP: Logged Mike Spaeth Phenomenal Film Handler Posts: 1129 From: Marietta, GA Registered: Jul 2000 posted 01-06-2003 04:35 PM                        If it is a Scope feature, make sure that the lens is set to the proper throw distance.  |  IP: Logged Tim Turner Film Handler Posts: 87 From: Chula Vista, CA, USA Registered: Jan 2002 posted 01-06-2003 04:36 PM                     We're using a STRONG projector. And so far we've only been running LOTR which is Scope. We haven't tried the flat lense yet, but I guess we should test a trailer or something. But so far the lense doesn't appear to be damaged.  |  IP: Logged Pat Moore Master Film Handler Posts: 363 Registered: Mar 2000 posted 01-06-2003 04:37 PM                     Tim -- I'm assuming that this occurs with all films, right? Did it just suddenly occur, or gradually appear over a period of time? With both Flat and Scope lenses? If it's both lenses and all film formats, that tells you the problem is likely projector oriented and not in lenses. Can you get the left side sharp with the focus knob? If that's the case, there may be a problem with the lens turret and its alignment with the trap. However, this would probably show up more with the picture being out of alignment with the screen and masking. If the picture is still properly centered on screen, then the problem might be in the film gate and trap. Depending on the projector, you need to be sure the Gate is closing fully on both sides of the film. Georgio's comment on the port glass is a good one. You could oil or some other problem that is effecting only part of the picture. Pat EDIT -- just saw your post that it's a "Strong" projector. I'm going to guess it's a Simplex Millennium. Check out the Flat lens image quality, and the porthole is a great candidate for causing a soft focus on one side of the picture. Other than that, the info above is a good start.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 01-06-2003 04:37 PM                     If it used to be in focus then the film plane is probably somehow not square to the lens. Check another lens though, it isn't unusual for a ring to be loosened during cleaning allowing the front or rear element to sit cockeyed. It may be a turret problem, you don't say if you have a turret or fixed lens mount. Rough treatment of the turret can misalign it and result in this focus problem, but that also shifts the image quite a bit. Usually the main complaint is that there's no image on one side of the screen... if that gets "fixed" by moving the projector (or recutting the aperture...) you'll notice the focus trouble. Take a good look at the film running through the gate. Any problem with the actual film being out of proper alignment should be visible. You should be able to tell by hand if the fixed gate or rail assembly is loose. If so, the pressure from the bands or whatever will push the thing off-square but hold it fairly steady so the image has a focus problem rather than shaking about. I would check if anyone has "fixed" the projector recently. That's usually my first question on odd problems like this. It's easy to fix a symptom without realizing the true problem, plus even proper periodic maintenance has risks - if parts were removed for cleaning or anything they may be improperly reinstalled.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-06-2003 05:24 PM                     Which of your simplexs is it the one with the old style manual turret of the electric turreted ones If you can bring each side into focus(and the other side then goes out I would check the gate bands as one is likely stretched or worn If it the old manual turret machine with the straight gate then probably the rail is worn. If you cannot bring that side into focus (even loosing centre and the focus on the other side) then I would bet the lens has been damaged (scorched) or the lamp alignment is off  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 01-06-2003 06:56 PM                     Plugged rails and/or bands with film wax and dirt buildup, out-of-alignment lens holder, warped film trap, or something binding in the focus assy, such as that Century, Cineshitty, Monee, or Westrex uses. Also, loose elements in the lens will cause that. I agree with Gordon's assesment on the lamp being mis-aligned.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-06-2003 08:01 PM                     Aside from what everyone else mentioned I've seen the lens element rings, and or the element assemblys come loose inside the back up lens. This can also cause some wierd uneven focus problems. Also make sure the lens does not have a shattered element inside it. This too will cause an uneven focus problem. Mark @ CLACO  |  IP: Logged German Marin Expert Film Handler Posts: 227 From: Verbania (VB), Italy Registered: Jul 2001 posted 01-06-2003 08:54 PM                     I had the same problem. We bought an Align-O-Tron and we notice that the projector was out of alignment, the laser was pointing up to the left. For our luck was not necesary change the mask.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 01-06-2003 09:16 PM                        First and easiest things to check and remedy are gate cleanliness (no buildup) and gate tension. Check turret (if one is used) or lens mount to be sure they are in proper position, and haven't gotten out of alignment. Likewise, check lateral guide rollers and studio guides to be sure they are properly aligned and aren't "pinching" the film. Gate bands and/or rails need to press uniformly on both sides of the film. Is the gate closing properly, or is there some binding? As others have noted, if both lenses have the same problem, it's not likely the lens. Try a lens from a different projector if you suspect both lenses got damaged by heat or careless handling. Ideally, you should see the finer resolution lines on the SMPTE 35-PA (RP40) test film, with any focus fall-off uniformly out at the edges. Greater than 80 line pairs per millimeter is ideal. Anything less than 40 is pretty bad.  |  IP: Logged Manuel Francisco Valencia Expert Film Handler Posts: 151 From: Oklahoma City, OK, USA Registered: Dec 2000 posted 01-06-2003 10:58 PM                     I think John has got it with the guide rollers. Check to see that they are spinning and have a little lateral movement.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 01-06-2003 11:09 PM                     If swapping the lens like John suggested does not correct the problem, I would advise inspecting the runner shoe contact with the bands to make sure they are making an even contact with the inboard and outboard bands AT THE SAME TIME when you very gently and slowly close the film trap without any film in it. If one side hits before the other side, that's your problem. You will need a very keen eye to see that. I have had that happen once on an XL with a curved gate, and the guide shafts that the trap assy slides on were actually bent. I removed the trap and used a nut driver to give the shafts a "wang" to straighten them. The problem went away. I hope you don't have to do this, because if you put too much butt behind the "wang" and if is sprung bad enough, you might wind up with a handful of peanuts!  |  IP: Logged

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