Film-Tech Forum ARCHIVE: Persistent focus problems, need advice

This is topic Persistent focus problems, need advice in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mark Farr-Nash (Member # 4233) on 04-24-2010, 09:42 PM:

Hey folks,

Been a while since I've been here. Things have been good, but I'm stumped with this one. I've got a scope lens that suddenly doesn't want to focus. It gets REAL CLOSE and then fuzzies up again. Here's what I've tried to do:

I changed gates (on my machine, it's worked before with jumpy film)

I loosened the lens and unwound my manual focus knob all the way back out again, and then centered it in the middle of the bolt, for the most amount of back and forth play.

I checked the lens for a burn spot or a crack (and while I was there, cleaned it)

I cleaned my glass plate (it was a little dusty)

I have loosened up the gate a little bit (this isn't a pinching or a jumping problem, but I thought I would try it anyway)

I have unscrewed the 2mm bolt that holds my outer focus ring in place and I have spent the last ten minutes trying to fine tune it from my REAL CLOSE position.

I'm really at my wit's end. Up here in Vernon, technicians are four to seven hours away, so I'm used to doing this for myself, but I'm out of ideas. Any suggestions would be most helpful.

Mark

Posted by Steve Guttag (Member # 268) on 04-24-2010, 09:56 PM:

Make and model of the lens would help. If it is a schneider, particularly ones of the '80s and '90s, odds are, the elements inside have twisted. They will never focus after that until they are realigned on an optical bench. Schneider lenses of that era are notorious for this.

I have not had that problem with the current generation of lenses or their integrated anamorphics, like the ES.

Steve

Posted by Mark Farr-Nash (Member # 4233) on 04-24-2010, 10:05 PM:

From what's on the front of the lens, the make is:
ISCO-GOTTINGEN
ULTRA ANAMORPHIC MC 2X 44857

Does that help?

Also, do these things go bad, like grapefruits? Aside from cracking or browning, I mean.

Posted by Adam Martin (Member # 641) on 04-24-2010, 10:45 PM:

Have you tried Focusing anamorphics?

Posted by Mark Farr-Nash (Member # 4233) on 04-24-2010, 11:04 PM:

No I haven't. Thanks for passing this along. I'll give it a shot.

Since then, I've actually changed my lenses back the way I had them. This cleared up the problem on my blurring movie in theater #2, but the focus issue moved back to theater #1. Here's what's interesting, though: now the problem isn't as noticable. It's more in focus, but now I've got what appears to be a barely noticeable halo around everything. It's as if it's trying to be 3D or something. And focusing it one way moves the images further apart. Focusing it the other way brings them closer together, but then can't quite seem to lock into focus. It's more noticable on the bottom of the picture, but it's still there. I'll run the loops tomorrow before the shows, but in the meantime, does that additional bit of into help?

Posted by Martin McCaffery (Member # 37) on 04-24-2010, 11:08 PM:

Have you looked through the lens with your eyes? The haloing sounds like water vapor may have leaked into the lens. Had it happen here once. You look through the lens and it appears either fogged or haloed.

Anyway, it's an easy check before doing the above mentioned stuff. You'll have to send it in for a bench repair if it is water.

Posted by Tony Bandiera Jr (Member # 2365) on 04-24-2010, 11:25 PM:

Sounds to me like that anamorph has been dropped and has elements that are out of alignment.

Send it in for repair or pick up the anamporph I have up for sale in the Equipment listings here.

Posted by Mark Farr-Nash (Member # 4233) on 04-26-2010, 11:21 AM:

Update: I used my focus loop and followed the focusing anamorphoric instructions. Now, my loop is pretty damn old, but it seems to have worked just fine. I'll power it up tonight and see if it has helped.

What's baffling to me is that it should all of a sudden be so OUT of focus. I've checked with my projectionists, and neither one had dropped the lens. There are no dents or scuffs on it. In fact, it's probably the only piece of equipment aside from the projectors and platter that they ARE really careful with.

Is this something that happens over time, or do I just chalk it up to the charms and thrills of running an old theater?

Posted by Adam Martin (Member # 641) on 04-26-2010, 04:24 PM:

Is the lens in a turret? Are the projectionists using the lens to turn the turret?

Posted by Mark Farr-Nash (Member # 4233) on 04-26-2010, 07:00 PM:

I feel like a jackass not knowing to what that refers, but I'm contextualizing it and I'm pretty sure the answer is no. This is an old RCA projector that has the socket in front for the lens. It slides in, and then a couple of turns of a knob inside the housing locks the lens in place. A pin placed at the top of the housing on the outside keeps it vertically aligned.

Posted by Monte L Fullmer (Member # 2797) on 04-26-2010, 07:52 PM:

If he's saying "RCA", bet that's the soundhead which may have an old Brenkhert sitting on top of it, or something else..

If so, it's prob an old flat-trap projector..wonder if the trap rails are getting worn to hold the film flat causing focus issues..or just a ton of build-up in the trap area which would prevent film to lay flat in the machine....

..just some guesses .. (for when he said "RCA", first thing that came to mind was RCA 16mm units ...)

_Monte

Posted by Mark Farr-Nash (Member # 4233) on 04-26-2010, 09:07 PM:

Second Update: Ran the print tonight, and lo and behold, I correctly focused the thing! Picture looks great now.

Now, all I need is a 2mm screw to replace the one that dropped on the floor and vanished...

Wow, I used my diagnostic loop to correct the anamorphic lens, and last week, I changed the lamp out at the beginning of a show, in five minutes.

...does this make me officially a projectionist, now?

Posted by Monte L Fullmer (Member # 2797) on 04-27-2010, 12:49 AM:

...more like a location booth tech/projectionist...

Posted by Sean McKinnon (Member # 612) on 04-27-2010, 09:06 AM:

I beleive RCA sold a re-branded version of the brenkert (or maybe it was a simplex i don't remember)

Posted by Mark Farr-Nash (Member # 4233) on 04-27-2010, 10:51 AM:

Monte, I can live with that!

These forums have helped and continue to help me. Thanks to everyone who generously gives of their time and expertise to be here and post. It's places like this that re-affirm my faith in the Interwebs (and people, too).

Posted by Monte L Fullmer (Member # 2797) on 04-27-2010, 01:20 PM:

quote:
I can live with that!

It's how I got started, and probably how a bunch of us got started by diving head first into the unknown...

(with help from studying machine/parts manuals..)

Good luck - Monte

Posted by Ian Parfrey (Member # 5122) on 04-27-2010, 02:08 PM:

Sean.

Yep, it's the Brenkerts.