8mm Forum: Image Ghosting

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Topic: Image Ghosting

David Roberts
Master Film Handler

Posts: 405
From: Suffolk. England
Registered: Apr 2004

posted April 07, 2019 08:53 AM

My Bauer 502 is ghosting on forward projection,and is worse in reverse. the loops are good and the picture otherwise steady.
Also,the sound of the mechanism is normal.
any ideas please.

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Leon Norris
Jedi Master Film Handler

Posts: 958
From: Elkins Park, PA, USA
Registered: Jun 2012

posted April 07, 2019 09:22 AM

David, it sounds like a shutter problem? You have to reset it! Also how is the speed is it running slow?

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Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted April 07, 2019 09:24 AM

Hi David...I'm familiar with the term "ghosting" in regards to telecine transfers. This occurs when the shutter is out of sync with the video camera and frames get blended during the recording. This frame blending produces an offset double image. If frames are being blended during projection...I can only guess that the timing of the pull-down of the shutter is out of sync with the rotation of the shutter. I have never seen this occur with other projectors, but perhaps cleaning and lubrication of the gate and the moving parts of the shutter and claw might help. I'm not familiar with Bauer machines, but maybe someone who is can offer more insight to an adustment for this problem.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted April 07, 2019 09:40 AM

As regards ghosting and the adjustment of the shutter, you should remember the word BRAT.
Below Retard. Advance Top.

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Maurice

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David Roberts
Master Film Handler

Posts: 405
From: Suffolk. England
Registered: Apr 2004

posted April 08, 2019 02:04 AM

Thanks for the advice offered.
This is a shutter issue ,its just that I don't know how to adjust the shutter on these.
I have a workshop manual,but it doesn't seem to cover this adjustment.
Has anyone worked on these series of projectors?Any of the 500 or 600 models will be the same How do you adjust the shutter in relation to the claw pull down?
Thankyou.

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Chip Gelmini
Phenomenal Film Handler

Posts: 1733
From: Brooksville, FL
Registered: Jun 2003

posted April 12, 2019 04:43 PM

I have timed shutters on 35mm projectors. Basically the frame should be 1/2 advanced and the shutter blade should be 100% blocking the light to the screen.

So when the frame is 100% stopped in motion the shutter will be open 100% as well. And remember it is doing this at 18 or 24 times per second.

How you adjust this on a super 8 machine I have no idea but basically this is what your goal should be.

I think Leon would agree partly on what I have written here.

CG

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David Roberts
Master Film Handler

Posts: 405
From: Suffolk. England
Registered: Apr 2004

posted April 15, 2019 01:45 PM

Thanks for the info.
Have decided my problem is the shutter cam,which is known to wear out on these Bauers.Shame,because I now have another with similar issues.
The shutter cam is plastic,and Edwin tried to 3d print them,but has had to stop because they could not be made to work well enough. Such a shame,but good that he tried.

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Maurizio Di Cintio
Jedi Master Film Handler

Posts: 977
From: Ortona, Italy
Registered: Jan 2004

posted April 15, 2019 04:18 PM

In super 8, cams are usually mechanically joint to their shutters so there is no way these assemblies develop any form of offset. However ghosting may occur all the same and this will happen if a slighthly worn cam is no longer able to cause the claw to retract perfectly after dragging a hole (frame); in that case film will be slightly moved upwards in the gate while the light is already on screen, until the film's resistance will prevent the sprocket to be dragged upwards any more. Then the claw will continue its movement freely before engaging a new hole and the process will start over.

If there is some highlighted element in the frame, this will be seen as "smudging" onto the neighbouring darker areas, simulating a ghost effect. This is usually to be experienced only at a very early stage of cam wear; as this progresses, the claw will be more and more hindered in its movement until it will cause damage to the sprockets. A way to deal with it (successful on Sankyo machines) is to move the whole cam assy slightly backwards in reference to the lamp: even half a millimiter should do, but this will not work forever it's just a temp hack. I am not sure it can be applied to Bauers as well...

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Maurizio

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David Roberts
Master Film Handler

Posts: 405
From: Suffolk. England
Registered: Apr 2004

posted April 16, 2019 01:39 PM

thanks Maurizio,
I know how to adjust the claw back and forward,in relation to the gate,and this has not changed anything.
I will continue to experiment,but am inclined to think its that shutter cam.

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