Author
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Topic: Projector problem?
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Tim Halloran
Junior
Posts: 14
From: Los Angeles, California
Registered: Mar 2006
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posted May 14, 2006 06:28 PM
Hello, I'm new to posting on this forum and was wondering if I could get some feedback from some of you experienced folks.
I've been using this Elmo ST600D projector for about a year now with no problems--or so I assumed. I project both old commercial films and my own stuff with this machine and as most of you probably know, it is bright and quiet and I was very happy with it. The lens on the projector is an "Elmo Super Zoom Lens, F:1.3, f=15-25mm." I always assumed that the image was really nice as I would just focus the projected image to what looked good to me and that was that.
But this past weekend an astute (and perhaps more "critical") viewer asked why the edges of the projected image "seemed to be slightly out of focus." So I adjusted the focus on the image so that the outer images indeed became very sharp. But to my great surprise, the center of the projected image went slightly out-of-focus. I then became obsessed with this repeatedly adjusting the focus back and forth. I could get the center of the image sharp (what I presume I have been doing up to this point), but the outer edges would go soft. If I sharpened the outer edges, the center would go slightly soft.
So my question is, is this just the nature of how this projector projects an image? Or is there something out of whack with the lens in there? The discrepancy in focus is ever so slight but I would think that it should be uniform across the projected picture plane, correct? Just for reference, I project at approximately 13 feet onto an old beaded DaLite screen. The screen is in excellent shape, however, with a perfectly even surface. Don't know if this matters but I thought I'd let you know.
Any thoughts or ideas about this? Is this something that can be remedied or is it something that is just a part of projecting 8mm film? Thanks in advance for your time.
Tim
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Jan Bister
Darth 8mm
Posts: 2629
From: Ohio, USA
Registered: Jan 2005
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posted May 14, 2006 07:47 PM
Hi Tim, welcome
Let's see... there are several possible reasons. For starters, I'm assuming that your projector is more or less centered toward the screen so as to avoid any noticeable keystoning effect (the rectangular shape of the projected image going trapezoid). But that's a very unlikely reason for the focus issue anyway. Does this happen with all of your films or only certain ones? If only certain ones, this suggests that the films in question are on the dry/brittle side and should benefit from a treatment with FilmRenew to allow them to run more smoothly through the machine. If it happens all the time: 1. The film gate pressure plate may have insufficient pressure because the springs have weakened over time. Remedy, remove them, stretch and re-install, but careful not to have too much pressure or the film might chatter, lose its loop and/or be damaged by the claw. 2. The gate itself has gone slightly out of alignment, so film either bows or warps very gently to the side as it runs through the film path, causing it to no longer run flat through the gate. 3. The projection lens (or its holder) is loose and needs tightening.
Hope this is of some help, for starters. Good luck
-------------------- Call me Phoenix. *dusts off the ashes*
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted May 16, 2006 08:02 AM
The lens 'slop' on my GS is between the outside diameter of the lens and the inside diameter of the lens housing on the projector. This is why I much prefer the Eumig projector designs where the lens is spring loaded into a v-groove, so the lens is uniquely located and cannot move around. True, the Eumig's do not have the hinged lens housing (so gate cleaning is a bit more of a fuss), but it does'nt need it as the v-groove is precision machined to be exactly perpendicular to the plane of the gate. The Elmo design is essentially a cylinder(the lens) located within another cylinder(the lens housing) so it cannot be precisely located and can slop around. Those little machined 'flat strips' on the inside of the lens housing are an attempt at a 'v-groove' location feature, but it is very poor compared with that big machined 'V' on the Eumig's. [ May 16, 2006, 07:38 PM: Message edited by: Paul Adsett ]
-------------------- The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection, Elmo GS1200 f1.0 2-blade Eumig S938 Stereo f1.0 Ektar Panasonic PT-AE4000U digital pj
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Graham Ritchie
Film God
Posts: 4001
From: New Zealand
Registered: Feb 2006
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posted May 17, 2006 12:29 AM
Hi Tim An easy and quick way to check you lens alinement is to run you projector without film,lamp on,zoom down to a acceptable size, check on screen that as you move your focus in and out that both your left and right edges which is your apature plate you are seeing on the screen,both go in and out of focus evenly,as an example say your left side is in focus but you have to adjust it to achive the same on the right then your lens is out of alinement,what you are trying to achive is an eveness of focus on the left and right edges,to obtain this there should be a small screw that acts as a stop situated at the bottom of the lens holder, adjusting this in or out should correct it,if after running film through the projector you find that both left and right are in focus but the centre isn't,then the film is bowing in the gate, this can be due to the film itself,to much spring pressure on the edge of the film,the film might not be running true from the top sprocket or even the claw might be protruding to much, hopefully you won't have to go down this path and a simple lens alinement fixes it, hope some of this might help best of luck. Graham
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted May 17, 2006 06:57 AM
Hi Kev, No, but I used to! I first came across one about 30 years ago, just when I was getting into S8 film collecting. I rented it from a local A/V store, and the picture quality amazed me so I bought it off them. However, the sound quality was pretty bad compared to my Eumig 820 and it scratched film, so I got rid of it, but was foresighted enough to keep that fabulous lens . Kind of wish I had kept the whole machine right now, maybe I could have fixed it up. I have eited my post above to show a picture of a projector very similar to the M100. I will see if I can find an actual M100 pic to post.
-------------------- The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection, Elmo GS1200 f1.0 2-blade Eumig S938 Stereo f1.0 Ektar Panasonic PT-AE4000U digital pj
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