Film-Tech Forum ARCHIVE: How can it be out of focus only on one side of the screen?

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Posted by Tim Turner (Member # 1109) on 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?

Posted by Michael Brown (Member # 890) on 01-06-2003, 04:00 PM:

??

Make sure that the gate is clean.

Posted by Tim Turner (Member # 1109) on 01-06-2003, 04:02 PM:

Yes, we've checked the gate everything is clean.

Posted by Giorgio Volpi (Member # 1182) on 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.

Posted by Mike Spaeth (Member # 524) on 01-06-2003, 04:35 PM:

If it is a Scope feature, make sure that the lens is set to the proper throw distance.

Posted by Tim Turner (Member # 1109) on 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.

Posted by Pat Moore (Member # 380) on 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.

Posted by Dave Macaulay (Member # 813) on 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.

Posted by Gordon McLeod (Member # 33) on 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

Posted by Paul G. Thompson (Member # 655) on 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.

Posted by Mark Gulbrandsen (Member # 72) on 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

Posted by German Marin (Member # 918) on 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.

Posted by John Pytlak (Member # 331) on 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.

Posted by Manuel Francisco Valencia (Member # 710) on 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.

Posted by Paul G. Thompson (Member # 655) on 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! [Eek!]

Posted by Rick Long (Member # 213) on 01-07-2003, 03:58 AM:

Maybe just cleaning the finger-prints off the lens?

Posted by John Pytlak (Member # 331) on 01-07-2003, 07:19 AM:

Usually dirt, fingerprints, or haze on optics (lens or port glass) produces contrast-reducing flare, but a severe fall-off in resolution on one side would not be a typical symptom.

Posted by David Stambaugh (Member # 1102) on 01-07-2003, 11:20 AM:

I remember seeing "The Player" with this problem. The image was focused on the left and right, but obviously very soft in the center. I complained, but they were not able to fix it.

Posted by Pat Moore (Member # 380) on 01-07-2003, 08:06 PM:

So Tim, what did you find out?

Pat

Posted by Nathan Guerriero (Member # 1214) on 01-07-2003, 08:23 PM:

I had this very problem on one of my screens with a century JJ. The culprit turned out to be a gate straps that would not stay aligned due to a bent film gate. It was easily, though not cheaply, remedied. I am still, symied, however, on one final question: WHO BENT THE FILM GATE???

Posted by Tim Turner (Member # 1109) on 01-07-2003, 09:31 PM:

quote:
Originally posted by Pat Moore.So Tim, what did you find out?
Pat

Well I'm still taking in all this information. You are guys are wonderful! I will pass all this along to the head projectionist.

Is there a diagram around of a film gate that lists all the parts and pecies I need to look for?
This is a Simplex TU-2000 with a manual lense turret.

Also is it possible for the heat from the lamp to damage the lense. If the changeover is open? I've seen this happen before and I know how hot that lamp can get.

Posted by Joe Redifer (Member # 3) on 01-07-2003, 09:40 PM:

It is VERY possible for heat from the lamp to damage the lens, but I don't imagine it would damage it in that fashion. I could be wrong. Heat damage from the lamp usually results in a very hazy low-contrast screen image.

Posted by Daniel Boisson (Member # 1027) on 01-07-2003, 11:01 PM:

we have this problem with one of our screens, our tech said the lens *might* have been fried at one point in the past, damaging the anamorph, although this particular lens is a very cheap one...

Posted by Gordon McLeod (Member # 33) on 01-08-2003, 01:50 AM:

That manual turreted head is a bit on the ruff side at best and from what i was told had a checkered history. Most likely culprit are the gate rails and the lens. The rails were worn when I was there in the spring. The lens wouldn't like the eposure to white light from an open dowser especially since the bigger lamp was installed then.
When I put the larger lamp in I did realign the lamphouse and the light on the screen was about 85% side to side so a hot spot should not be an isue unless it has been adjusted since then

Posted by Randy Stankey (Member # 64) on 01-08-2003, 10:31 AM:

While the film is running, put your hand on the lens turret, as if you were going to open it. Gently try to push the turret open and shut. (Wiggle it.)

If you find play, the turret will be out of alignment, thus moving the lense(s) off center with the film plane. The lens(es) MUST be perfectly perpendicular with the film plane or you will get a partial "out of focus" position as you describe.

The solution is simple. Have your technician or head projectionist realign and tighten the screw(s) that hold the turret shut. This is literally a screwdriver-type job. It can take just a minute or two to complete... But it MUST be done properly or else you might mess up more things than you fix.

When I have had reports of this problem in the past, this is the first thing I would ask... "Does the turret move?" If it did, I had a 90% chance that this was the problem.

Of course, there are many other things that can cause this but this is one of the simplest and easiest to fix.
Always check the simple stuff first. [Big Grin]

Posted by Tim Turner (Member # 1109) on 01-13-2003, 11:44 AM:

Ok just an update here. The problem seems to have been found, but we are unable to test it out due to fear of Electrocusion [Big Grin]

So I'll ask you guys if this could be the cause of the blurred left side of the screen.

Yesterday, the lamphouse would not power up, and when we opened it we found that that thin sheet of metal that gets blown by the exhaust fan had become stuck in one position. Wiggling that got the lamp to strike. But We also noticed that the Binding Post and Positive Lead Ass'y, where that ground wire of the Xenon lamp plugs into was severly burne. Infact there was a big hole burned right in the middle of it, and the ground wire was slowly sinking right through it.
The burning looks like it had been happening over a period of time.
Any dust and ashes from the binding post (Is is called a Gadsket
?) where all over the place, including the Mirror, and we think that is whats might be causing the the blurred image. But we are unsure because we've learned that the insenertated binding post is a major problem and if the ground sinks too far down and touches a metal part of the projector, the projectionist might fry operating the projector!

Could this be the cause of the blurry screen?
And what the heck could have caused the burning of the Binding Post and Positive Lead Ass'y?

Posted by Paul G. Thompson (Member # 655) on 01-13-2003, 01:12 PM:

Possibly. It sounds like the bulb may have been far enough out of alignment causing the film to buckle in one side of the film trap. Chances are, you had one heck-of-a-hot-spot on the screen. What I mean by that is the illumination of the screen from side to side and top to bottom was not even.

Posted by Mark Gulbrandsen (Member # 72) on 01-13-2003, 02:04 PM:

Tim,
Best idea is to replace all those burned up parts, do a proper bulb alignment, and see how it looks then. If ya don't get the parts replaced you may well be completely off the screen soon!
Mark @ CLACO

Posted by Ken McFall (Member # 845) on 01-13-2003, 08:59 PM:

Paul...

Cineshitty.....

what make is that, never heard of it, is it american by any chance. Got any pics to share? [Big Grin]

Posted by Daryl C. W. O'Shea (Member # 1303) on 01-13-2003, 09:00 PM:

Ken, I believe Paul was referring to the Italian Shakeameccanica. [Smile]

Posted by Ken McFall (Member # 845) on 01-13-2003, 09:07 PM:

Tim...

the burnt connector had probably worked loose over time, or was never tight in the first place. All connections should always be 'Bright & Tight' or they will create a local resistance which will cause them to heat up, so the resistance increases so it heats up more and more until it burns out.

The gasket you talked about is vital to the correct operation of the strike circuit of the lamphouse to prevent the high voltage required to strike the lamp from jumping to ground.

No offence but you sound as if you are not the right guy to be attempting repairs to the equipment and you should get an engineer in as soon as possible. If you do, then watch him and ask lots of questions so you can watch out for problems in the future.

For now get it repaired with the right parts for everyone's safety.

Good luck.

Posted by Ken McFall (Member # 845) on 01-13-2003, 09:09 PM:

Daryl..... don't you start....

Posted by Daryl C. W. O'Shea (Member # 1303) on 01-13-2003, 09:27 PM:

Ken, I'm not starting... I always wanted to know what it'd be like to watch a movie on a small boat in the middle of the ocean during a really big storm. [Smile]

Posted by Ken McFall (Member # 845) on 01-13-2003, 09:35 PM:

I'm gonna retire to my corner deeply wounded by that [Frown]

Watch out or I'll steal your paddle so you can't get back!

Maybe I've got the shakes and don't see it myself..... [Big Grin]

Posted by Gordon McLeod (Member # 33) on 01-13-2003, 09:50 PM:

That connector was like tht for some time. It would not be the cause of the focus problem. The connections are actually still sound and isolated from the case

Posted by Ken McFall (Member # 845) on 01-13-2003, 09:56 PM:

Gordon,

from the sound of it all the equipment is in need of a good service. If the air vane is filthy and sticking then the chances are the supply and extract fans are the same and not doing their job correctly.....

Posted by Tim Turner (Member # 1109) on 01-13-2003, 11:56 PM:

I'm most definetly not the right guy to be attempting repairs such as this. And I wouldn't try it either. I wish I could though.

Posted by Ken McFall (Member # 845) on 01-14-2003, 12:51 PM:

Given time and an understanding helpful engineer you'll be surprosed how much you can learn.... so take it easy, watch, listen and learn.

Regards Ken.

Posted by Gordon McLeod (Member # 33) on 01-14-2003, 09:26 PM:

Actually I know the exhaust is now working as I spent a day on the roof with the mech contractor as they were causeing a NC issue dueing recert testing