8mm Forum: Focusing Frustration

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Posted by Paul Adsett (Member # 25) on November 25, 2009, 12:58 PM:

What is it about Elmo projectors that keeps you fiddling with the focusing knob during the film? Both my GS1200'S seem to have 'rubbery' focusing, you can never seem to get that razor sharp condition across all areas of the screen at the same time, and if you do, it does not seem to stay that way for very long. So showing films on a GS, at least for me, means riding the focusing knob during the reel.
Contrast that with my Eumig's which seem to really 'snap' into sharp focus and then stay that way throughout the reel.

Posted by Michael O'Regan (Member # 938) on November 25, 2009, 02:07 PM:

Is this problem common to all Elmos or just the GS?

Posted by Douglas Meltzer (Member # 28) on November 25, 2009, 05:12 PM:

Paul,

Sorry, but I don't have that problem on either my standard GS or the xenon model. Strangely enough, I had a Eumig which suffered from that!

Doug

Posted by Tony Milman (Member # 7) on November 25, 2009, 05:23 PM:

Neither do I but maybe that's my eye sight

Posted by Graham Sinden (Member # 431) on November 25, 2009, 05:34 PM:

Paul, I know how you feel but I always put that down to using the Elmo 1.0 lens which is affected by the heat. Try a 1.3 and it might be better.

Just what has happened to your photo??

Graham S

Posted by Joe Taffis (Member # 4) on November 25, 2009, 05:46 PM:

Graham S....what's that about the heat affecting the Elmo 1.0 lense?

[ November 27, 2009, 03:14 PM: Message edited by: Joe Taffis ]

Posted by Graham Ritchie (Member # 559) on November 25, 2009, 07:26 PM:

Paul
Is it possible it could be down to a bit of film shrinkage on some prints. I do have films that are perfect where you can focus and leave others not so.

Also I think one of the problems with Super8 is that it has a short depth of focus with its small frame area compared with 16mm so any slight change of shape on the film going through the gate can look quite bad, myself I usually sit next to the projector for those focus adjustments where as with much of my 16mm I dont.

Graham.

Posted by David Kilderry (Member # 549) on November 25, 2009, 08:28 PM:

It is a well known Elmo weakness that I am sure has been discussed here before.

Every one of my Elmo 1200 series projectors has suffered from it. The focusing system is less than precise especially compared to the Eumig 900 series.

Sankyo projectors suffer from it as well; simply too much slop and with wear, free play in their focus adjustment design.

This is one area where the Eumig beats the Elmo hands down.

David

Posted by Paul Adsett (Member # 25) on November 26, 2009, 09:36 AM:

I think you are right David. The lens is just not held very tightly or very precisely on the Elmo's - when you focus you can actually see the lens rock a little from side to side. Also, there is insufficient spring force to bias the lens against the snail cam, so you end up with a huge amount of 'backlash' when you rotate the lens knob.
On the Eumigs, the lens is heavily sprung into a 'v-block' which is precision machined directly into the chassis and exactly perpendicular to the plane of the gate, and there is a really strong spring to push the lens against the snail cam - so there is no lens wobble at all.
Does anybody have a procedure for setting up the lens on the GS1200? I know that you adjust the little screw by the gate for side-to-side focus, and loosen the two lens mount screws to adjust top-to-bottom focus, but this is a real hit and miss adjustment because there is so much 'cross-talk' between them How exactly are you supposed to do this?

Posted by Brad Miller (Member # 2) on November 26, 2009, 12:00 PM:

Short of getting some actual SMPTE target film, you can get some K40 and make your own. Just get a large pattern of thin vertical and horizontal lines drawn as big as you can get (as in, wall-sized if possible) and film it. When you get it back from the lab, you will have something you can use as a reference to obtain ideal lens adjustment on. Just make absolute sure when you filmed it that the camera was perfectly centered both horizontally and vertically to the "wall target".

If someone on the forum was enterprising, I'll bet quite a few people here would want a 50 foot roll of this.

Adding forced air cooling to the gate also works wonders for keeping the film from buckling if you have too much heat from a large lamp, although if you are using a stock Elmo 250W lamp I doubt you need it. I would look at the barrel alignment more than anything.

Posted by Joe Taffis (Member # 4) on November 26, 2009, 03:36 PM:

I use a SMPTE test film. Steve Osborne at THE REEL IMAGE sells them for around $25.00.

Posted by John Hourigan (Member # 111) on November 26, 2009, 11:33 PM:

Paul, I agree with you -- focusing seemed to be more precise (and more "stable") on my Eumig versus my Elmos. I find that I have to "ride" the focus knob on my Elmos, which does take some fun out of running film shows.

Posted by Brad Kimball (Member # 5) on November 27, 2009, 03:56 PM:

I have some B&H 2500 series untis (16mm) that all suffer from the same problem. I have to tape the focus knobs on all of them in order to not have to hold the knob still throughout a movie.

Posted by Graham Sinden (Member # 431) on November 27, 2009, 04:55 PM:

Joe, Im not sure what I said was correct but I was always told that the elmo 1.0 lens is much harder to focus (and keep in focus) than the standard 1.3 due to the way its built and the sensitivity. However its a long time since I used the old 1.3 lens so its difficult to compare the two.

Dont know if its the same as SMPTE film but Derann sold their 'Scope alignment Reel' on a 50ft reel

Graham S

Posted by Thomas Murin, Jr. (Member # 1745) on November 27, 2009, 04:56 PM:

My B&H DCM suffers from this. Yet, I had the lens out yesterday before a screening to give everything a good cleaning and when I was running the show, I only had to adjust the focus at the beginning of each reel.

Not sure what I did but I hope it lasts!

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