8mm Forum: Elmo GP-E lens flecks >:-(

This is topic Elmo GP-E lens flecks >:-( in forum 8mm Forum at 8mm Forum.

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Posted by Richard Kemp (Member # 1621) on January 28, 2010, 10:31 AM:

Hi,

Been here before (subject) and it isn't getting any easier :-o Have just noticed several lens specks on a newly acquired Elmo GP-E. Projector bought to replace another GP-E with *exactly* this problem ~ this projector seems to be prone to dusty lenses? The specks are inside the lens right enough. Last time I tried to open one of these I ended up with a lap full of optics and goodbye lens. Is there a knack to cleaning out one of these lenses (multi optic) or should I find a specialist and is there any guarantee that anyone can fix this optic glitch please?

[sigh]

Many thanks

Posted by Richard Kemp (Member # 1621) on January 29, 2010, 02:49 PM:

Hi,

Here is a front view through the Elmo 1.3 zoom lens, two views of the same particle.

http://i124.photobucket.com/albums/p32/r_i_c_2007/GP-E3copy.jpg

Any tips on clearing these flecks (there are several, only one shows up in the photo)would be greatly appreciated.

This is my second GP-E lens with exactly the same problem [Frown]

Many thanks

Posted by John Davis (Member # 1184) on January 29, 2010, 03:00 PM:

Hi Richard,
I can't offer any cleaning advice, but can I ask do you notice any significant drop in image quality?
I know from my own optics which I think are quite clean; as soon as I switch the lamp on the lens looks terrible, but the projected image is fine.
John

Posted by Richard Kemp (Member # 1621) on January 29, 2010, 04:44 PM:

This is the problem John, I use the projector for aerial transfer because I can control its speed and it doesn't jump film, but the transfers are marred if they have unsightly specks in them.

I have used a dreadfully mucky lens in the past but the problem was with the front optic, so the light tended to dissipate the build-up at that end of the lens; but if there is foreign matter towards the lens gate end of the lens its going to get projected along with the film imagery passing through the gate, and this seems to be the problem.

I still have the mucky lens but the projector behind it is a Chinon IQ 8811 which jumps and breaks film, i really don't want to go back there again in a hurry :-o

Thanks

Posted by John Davis (Member # 1184) on January 29, 2010, 05:14 PM:

I see your point. If you can't find a suitable technician to get the lens clean, it may be cheaper trying to get another lens. As far as I know, the lens fitting on the GP-E is the same as all the subsequent machines and given the GP-E was an early 70s machine it's possible that this characteristic was sorted in later lenses.

Posted by Richard Kemp (Member # 1621) on January 30, 2010, 06:36 AM:

Thanks John,

Spent an age last year hunting down lenses for my first GP-E and got nowhere fast - as it is the correct lens is quite difficult to remove and install anyway (tight fit) and similar lenses gave shocking results. I'm going to bite the bullet and take the lens into a specialist who will either clean it or tell me it cannot be cleaned, putting me out of my misery one way or the other (hope) - in which case I will customise the second GP-E projector for transfer which is currently standing idle (no lens at all). If all fails I am back to square 1 looking for another projector - a sound projector this time, for improved constant speed setting.

Bests

Posted by Martin Jones (Member # 1163) on January 30, 2010, 06:48 AM:

Just my penn'orth, Richard, but going down the road of transferring direct from the gate (no projection lens and no field lens involved) is a definite improvement, and if your can "flip" the result laterally without using a mirror, better still.
Martin.

Posted by Richard Kemp (Member # 1621) on January 30, 2010, 03:49 PM:

Hi Martin,

Gosh, I had never even considered that! :-o

I imagine you would need a pretty powerful capture cam zoom to work with the lenseless film gate? I think mine is about 20x which gives me just about enough zoom to frame the gate neatly, but that's cam-ing down a projector lens.

I took the GP-E lens to 'DP' at Mr Cad's of Croydon (South London) < http://www.mrcad.co.uk/shop/home.php > who said the marks weren't dust (or internal) but scratches. This amazed me. Then he spent some time polishing the rear optic with optical cloth and announced he could then hardly see any marks ... then he said he could still see one. I had a look with his lube but it was impossible to verify what he was saying because I used a magnifying glass against a neg viewer so couldn't 'get my bearings' standing inside a shop holding the lens up to a window, but I couldn't see any dots either.

He gave me the private contact details of a local lens specialist in case I wanted to pursue the matter further. I now need to put the lens through its paces again, I will soon know if the problem has persisted. I have a Regular 8 film coming back from Europe where they have split it for me, I may wait for that to arrive before I set up my transfer arrangement again (which takes much time and not a little blue language) in order to make a fresh transfer then scrutinise it for static 'black dots'.

But please update me on your lenseless system!

Many thanks

Posted by Martin Jones (Member # 1163) on January 31, 2010, 03:20 AM:

Richard,
This will give you an insight into the basics http://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=8;t=000936#000000

Lots of us are now using this approach in one form or another. The big advantage is that the projection lens (which is usually of relatively poor quality) is replaced by a "supplementary" lens, which could be (for example) a 35mm SLR lens of far superior quality.

Martin

Posted by frank arnstein (Member # 330) on January 31, 2010, 04:54 AM:

Hi Martin
I read your interesting report & was very impressed with the way you have solved the problem of shooting direct into the frame without loss of picture size, using the B&H projection lens as an intermediate lens.
Have you also tried using an LED light in place of the capsule 10w? Being cooler & having a directional beam, may be even better than the capsule type which would disperse light in all directions. Perhaps the LED would be too bright ???

Dogtor Frankarnstein

[Eek!]

Posted by Martin Jones (Member # 1163) on January 31, 2010, 05:13 AM:

My capsule light has a diffuser between it and the lens, which turns it into a "back-light" for the film rather than a projection lamp. What light is radiated in other directions does not enter into the equation and is therefore irrelevant. Colour temperature is fine and the choice of lamp wattage brings it within the range that the pickup camera can easily handle. And it's cheap and simple.
Others use LEDs, ranging from simple single white ones to complex arrays of multiple LEDs in the three primary colours to allow subtle variations in colour temperature. All those can be brightness controlled by varying the current. All of those LED solutions are relatively expensive compared to the simple Halogen lamp approach; my new Mk 4 machine (currently under development) will probably use a single white LED, but still with a diffuser, however.

Martin

[ January 31, 2010, 06:20 AM: Message edited by: Martin Jones ]

Posted by Richard Kemp (Member # 1621) on January 31, 2010, 07:33 AM:

Thanks Martin: like the idea of wiring a ciné projector into a computer by way of CineCap.

Btw: my light source is a 15 or 25watt bulb - wired separate from the projector - filtered through white perspex, which gives good results.

The other gremlin besides the lens is the GP-E motor which is struggling to hold 16.67fps. this is obviously bad news because these projectors were designed for 18-24fps. am wondering if some basic maintenance might improve the motor's performance? this is the main reason i'm toying with converting the spare GP-E to transfer, purely to utilise the (hopefully) healthier motor.

Thanks again

Posted by Martin Jones (Member # 1163) on January 31, 2010, 07:45 AM:

Richard,
I don't know the GP-E specifically, but if it is similar to a lot of the simpler specification Elmos in using a simple switch to select either of two presets to control a DC motor at 18 or 24 fps then the motor should be able to run at 16.667 fps comfortably if the RANGE of the 18 fps preset is MODIFIED to encompass the required speed. For that you would need the schematic of your machine so that the situation could be assessed.
I'm assuming that you have tried changing the speed using the preset and it will not quite reach 16.667 consistently; or did you mean something else?
For those wishing to use other machines, such as many Eumig models, there are circuits available to synchronize them to the video camera used for pickup.

Martin

Posted by Richard Kemp (Member # 1621) on January 31, 2010, 04:57 PM:

Thanks Martin,

I am a bit confused here because I altered the settings of the rheostat about a year ago to lower the speed, so in theory I should have a 16fps-24fps speed spectrum but the projector motor reaches 'zero flicker' at top speed setting [=approx16.67] and begins just recently to falter momentarily, generating a flutter across the screen. After half way through a reel this faltering ceases and all is plain sailing, but obviously i fear motor melt-down for unknown reasons, if the motor is struggling so far below its optimal setting. Is it possible the rheostat has somehow slipped since I altered it?

Posted by Martin Jones (Member # 1163) on February 03, 2010, 05:26 AM:

The setting is not likely to have slipped, so I would assume that the problem may be a change in mechanical conditions (friction, belt slip etc). But I daren't go beyond speculating without physically handling the machine.
Perhaps, Kevin Faulkner can help as he knows considerably more than I do about Elmos

Martin

Posted by Richard Kemp (Member # 1621) on February 03, 2010, 12:28 PM:

Thanks Martin,

I had the cover off and can't see how I could have influenced the speed anyway - beyond what it's capable of - there is a steel sprocket (like the hand on a clock) which is stopped by a metal flange at the 12'o clock position on the reverse of the rheostat.

I need to set both GP-E's in motion and compare speeds.

The lens is just as bad as before - lube shows nothing - need magnifying glass against constant light source then revolve lens at angle until you can easily see black flecks around the edge and one near the centre: have no idea what the man in the shop was looking at, obviously something completely different which doesn't show up during projection anyway. I will send it off and cross fingers and thumbs.

Thanks again [Smile]

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