Film-Tech Forum ARCHIVE: Christie Focus Problem

This is topic Christie Focus Problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Robert E. Allen (Member # 1351) on 05-02-2007, 02:54 AM:

We have 15 Christie machines at our house and prior to coming here I'd run just about everything made EXCEPT Christie. I can't say I'm at all thrilled to get my hands on them. One of them has a focus drift problem in the flat mode. I mean it is constant requiring the operator to return to that machine every couple of minutes to correct the focus. I can stand there and watch it drift. I checked to see that the lens is tight in its mount and attempted to move it by hand but it's solid. So we moved the print to another maching and hung a "No Flat Prints" sign on the machine. There is no problem with scope prints on that machine.
Any advise? (I thought about putting the machine in the dumpster but realized I couldn't cover the cost on my salary.)

Posted by Brad Miller (Member # 2) on 05-02-2007, 03:10 AM:

Robert, the flat lens is probably not screwed tightly into its barrel. Remember even though the barrel of the lens is mounted tightly into the turret doesn't mean the actual lens element isn't working it's way loose with the vibration of the projector.

Posted by Monte L Fullmer (Member # 2797) on 05-02-2007, 03:23 AM:

...we run into that problem when the booth operators holler at my due to focus issues in SCOPE ... sure enough, the backup element lens barrel has came unscewed out of the mains barrel about half way.. Having manual turrets, they grab the rear of the scope lens and use it as a handle to swing the turret around..and not knowing that they are unscrewing the element barrel at the same time.

I remember a cinema that had the same flat focus issue with a PRO-35 'boat anchor' - horrible flat focus, til I found the element barrel was halfway unscrewed from the mains barrel and actually tipping upward when incerted into the lens holder..

-Monte

Posted by Alex Grueneberg (Member # 2652) on 05-02-2007, 04:35 AM:

Can loose glass elements in the flat lens cause drift at all? We've been having a similar issue.

Posted by Louis Bornwasser (Member # 3063) on 05-02-2007, 04:44 AM:

Easy way to prove it. Swap FLAT lens with another house; does it stay or go? Louis

Posted by Mark Gulbrandsen (Member # 72) on 05-02-2007, 08:03 AM:

quote: Robert E. Allen
We have 15 Christie machines at our house

WOW! One in each room... bedrooms, bathrooms and even in the kitchen [Big Grin]

.

If you stop and analyze the Christie and begin to understand it you will actually discover that its a dam good machine(assuming you don't have an older model with the shutter gearbox).

Mark

Posted by Ken Lackner (Member # 1002) on 05-02-2007, 11:01 AM:

quote: Alex Grueneberg
Can loose glass elements in the flat lens cause drift at all? We've been having a similar issue.

Absolutely. To determine if this is the case, remove the lens, hold it up to your ear, and give it a gentle shake. Hear anything? If so, then one (or more) of the glass elements is loose and the lens will need to be sent in for repair.

Posted by Mark Gulbrandsen (Member # 72) on 05-02-2007, 01:30 PM:

Actually even a local camera repair shop can tighten up the element lock rings with an appropriate lens spanner. Then apply a small dot of black paint to aid in locking that ring in place or it may loosen up on you again. Easy repair!

Mark

Posted by Robert E. Allen (Member # 1351) on 05-03-2007, 01:45 AM:

Thanks Brad et al. I'll check that out.