Film-Tech Forum ARCHIVE: Lenses

This is topic Lenses in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=010224

Posted by Michael Voiland (Member # 5386) on 12-21-2009, 05:05 AM:

So I read this in the tips section
http://www.film-tech.com/warehouse/tips/anamorphics/anamorphics.html
And
recently when I was working at our other theater someone took a presoakened lens tissue meant for a computer monitor and added more solution to it. They then proceeded to "clean" our scope lens. Now from what I have been able to work out some fluid got inside the lens and screwed it up. Then someone took apart the lens and cleaned it. Now it refuses to give me a good focus. Could the cause be that they just didn't refocus it. I can almost get a nice focus but it just looks pitiful sometimes. We played avatar and it was slightly blurred. I have never done work on lenses before but you need to start somewhere right.

Posted by Demetris Thoupis (Member # 833) on 12-21-2009, 06:13 AM:

In case your lens swings the anamorphic out of the way and you are left with the primary lens, focus fist the primary lens to get an even focus across the screen without the anamorphic down. THEN proceed with puting the anamorphic in place and focus until you get the sharpest image. Do not move the primary lens until you achieve the sharpest image possible from the anamorphic. If you cannot achieve a good focus, the your lens is fubar.
Demetris

Posted by Ian Parfrey (Member # 5122) on 12-21-2009, 06:13 AM:

Micheal.

It is often a pity when so called "knowledgable" people attempt simple jobs and end up making things much worse.

By the sound of your post, you may have one such person working at your location- and they should be banned, shot, exterminated and rendered sexually sterile so they may not procreate and further contaminate the gene pool they are a part of.

Lenses are, arguably, the most important link in the projection chain and exhibit the most effect on the image seen by the audience.

Anyone who is the least bit knowledgable in the area of projection knows the correct procedure in cleaning all lenses - prime, anamorphic and magnacom, and if they are in doubt, there are many charts and techniques recommended by lens manufacturers that are available.

As the lens referred to has breathed in moisture/solvent, and has been taken apart and reassembled, then the results you report indicate a very expensive doorstop is now the result. Lenses can not and should not be taken apart without the equipment and expertise in optics required to properly reassemble and recalibrate the lens. Lenses are manufactured to extremely fine tolerances and ultra-clean atmospheres and some lenses are also assembled with positive pressures internally to prevent vacuums inhaling oils and gases which then affect the resultant screen image.

I guess that I'm saying is that...

1. The incorrect cleaning solution was used to clean the lens.
2. The incorrect method was used in cleaning the lens.
3. Dissassembling the lens has allowed the factory atmosphere to escape and will make reassembly to factory spec almost impossible.

You have rightly observed that the lens was incorrectly cleaned, although without seeing the lens "in the flesh" makes it impossible to suggest anything but returning the lens to the manufacture for reassembly, realignment and possible recoating of the elements.

I hope that you have good luck in this, but I sense that your location will be up for either an expensive repair bill or a new anamorphic- neither of which is an ideal situation if only correct procedures were initially followed.

Posted by Louis Bornwasser (Member # 3063) on 12-21-2009, 07:41 PM:

What make/model lens? Louis

Posted by Mark Gulbrandsen (Member # 72) on 12-21-2009, 10:49 PM:

If it's a chneider or Isco anamorphic it should be sent back to Century Optics in Burbank. They are about the only optical house in the USA that can repair anamorphics. Takes special equipment and test projectors to align the elements once it's been disassembeled. If it's any other make of lens you no own an official booth door stop!

Mark

Posted by Monte L Fullmer (Member # 2797) on 12-22-2009, 12:35 AM:

Even jarring an anamorphic attachment can knock the elements out of kilter inside where it has to be sent back for realignment. If you can't get a good focus out of an attachment, this is what prob happened.

You gotsa lot of glass inside those things and they have all to be perfectly aligned right to look good.

Why I detest manual turrets on projectors when booth clowns slam the lens around for lens changes. This alone will knock things out of alignment.

-Monte

Posted by Michael Voiland (Member # 5386) on 12-22-2009, 02:02 AM:

So I still cant get a straight answer. But I did get part of an answer. I don't know who screwed up the cleaning but the lens cleaners they used were meant for glasses and computer monitors.
We have a swinging turret on a pro35. The flat lens was ok but my boss had to take the lens out of the holder and clean it as he said a Detailed Cleaning. He broke the lenses down into 3 pieces. Today at night I got a green strip and a trailer loop and went at it making sure the lenses was level. I think it was slightly turned. The focus is better and the image covers the screen in the bottom corner to the edge. We don't have any smtpe test film so when I see our booth tech in a week or two I will ask him to check it out. It can never be an easy problem - sigh -

-Mike

Posted by Monte L Fullmer (Member # 2797) on 12-22-2009, 02:12 AM:

Have you got a PRO35, MKVII unit - one with the common base lens mounted in the projector and the slider system where there is an magnicom lens for the flat and just the attachment for the anamorphic with both lenses in this slider unit?

quote: Michael Voiland
Could the cause be that they just didn't refocus it

betcha they got one of the elements inside turned around..or not centered correctly when they disassembled the unit..

Posted by Michael Voiland (Member # 5386) on 12-22-2009, 04:47 AM:

Is their a manual for the mark VIIs floating around anywhere. We have 4 of them. One doesn't swing open all the way and needs to be pushed open the rest of the way. 3 of the plate changers are semi working or busted and someone disconnected the motor that rotates the lenses. I see strong has a slider for multiple lenses but ours is a metal disk that rotates. its geared halfway along the side.

From going through strong cinema's website i found the turrets we have installed on our pro35s they are simplex tu2000e turrets.
the link is to the manual.
http://www.strong-cinema.com/DisplayFileObjects.aspx?i=7c70fded-f549-465d-aae0-d86b57f96872

Posted by Monte L Fullmer (Member # 2797) on 12-23-2009, 12:42 AM:

"You should not be here!" This is what pops up when that link posted is opened .. too funny!

Goto the manuals section on the left, scroll down in the "projector" section and you'll see the manual for the TU-2000 turret which also indicates parts listing.

Posted by Randy Stankey (Member # 64) on 12-23-2009, 08:58 AM:

Michael,

Have you tried Brad's instructions on focusing the anamorphic lens as described on the page you linked to?

If not, you need to do that (better still, have your tech do it) before you do anything else. If you are not sure the anamorphic is set up properly, nothing else will matter.

Now, if this has been done by a competent person and there is STILL a problem, then you can safely assume that one or both of the lenses are damaged or malfunctioning.

I say, "both" lenses because a "scope" lens is often made up of two separate lenses piggybacked together. You have the "prime" lens which is a normal lens of a specific focal length with a special anamorphic attachment on the front. That's what gives you the "unsqueezed" effect of the scope/anamorphic movie.

The anamorphic attachment can simply be unscrewed from the prime lens. It is possible that somebody "took them apart" to clean the two lens surfaces inside the unit as the two of them are screwed together.

You might think the lens has three pieces because one of them is just the mounting collar that holds the other two steady inside the projector. The other two parts would be the actual optical assemblies. I don't know for sure. It depends on the model of the projector.

IF that is what has been done, your solution could be simple.

All that needs to be done is to unscrew the scope attachment from the prime lens and ensure they are both clean on all four surfaces. If you have to use any tools to do this you are going too far. 90% of the time you can just use your hands. (There may be a little, tiny locking screw that holds the two lenses together. A jeweler's screwdriver is all that's needed to release that locking screw.)

Once you are sure the lens is clean, reassemble and follow the instructions on "How to focus an anamorphic lens."

If that works, you are in the clear.

IF that does NOT work, you have a problem that needs further attention.

Remember this: "Always try the simple solutions first!" [Smile]

Posted by Michael Voiland (Member # 5386) on 12-23-2009, 05:53 PM:

Thank you. I will have our tech look at it. I think the lens might have been turned slightly in the holder as focus has slightly improved. But I is still not that sharp focus that you are supposed to see. I don't have any standard test film so I will have our tech who i know does do it.

Posted by Dave Macaulay (Member # 813) on 12-24-2009, 08:12 AM:

If the image with just the backup lens (scope adapter swung out of the way) is sharp, you have to focus the scope adapter.
If someone unscrewed the front of the usual kind of scope adapter, the focus markings are probably wrong so you can't just set it to 100' if you have a 100' throw and get a decent approximation of correct focus. The threads that hold the front on have multiple starts, and getting the right start is not likely if you're just trying to get the thing back together. The focusing process is pretty simple but you do need a test image with sharp horizontal and vertical lines. If the picture is acceptable I would leave it for a tech with proper test film.

Posted by Michael Voiland (Member # 5386) on 12-26-2009, 01:25 AM:

Its acceptable but its still slightly fuzzed around the edges. When I get the tech out here then I will have him look at it.

Posted by Michael Voiland (Member # 5386) on 12-29-2009, 03:58 PM:

The booth tech came and disassembled cleaned and reassembled the lens. Its looks really sharp.

Posted by Randy Stankey (Member # 64) on 12-29-2009, 04:37 PM:

I guess we can safely assume that the anamorphic attachment was misadjusted or that there was dirt on a lens somewhere.

In which case, I suggest you get a baseball bat and keep in in the booth. The next time you see somebody fooling around with the adjustment on that lens you can take that bat and hit him upside the head with it!

[Wink]

Posted by Ian Parfrey (Member # 5122) on 12-29-2009, 04:43 PM:

...repeatedly, and with verve!