Film-Tech Forum ARCHIVE: Kelmar Lens Turret ajustment

This is topic Kelmar Lens Turret ajustment in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Paul Vollmers (Member # 927) on 02-22-2013, 03:30 PM:

A friend of mine has a Century SA with a kelmar lens Turret.
He has a scope lens, and a flat lens.
The screen throw is about 25 ft.
The scope lens fills the screen however when changing to the flat lens it is offset to the left by about 12 inches off center on the screen.
Is there an adjustment of some kind to center both pictures on the screen?
I looked up the manual on Film-Tech but there is no mention of centering both lenses?
Any help here?

Posted by Louis Bornwasser (Member # 3063) on 02-22-2013, 05:01 PM:

Yes. First determine which lens is correct and leave it alone. Use an alignment tool. Remember that the lens is NOT in the center of the film; it is offset by half the soundtrack width.

When one lens is correct, project image and mark center of test chart on screen. Rotate to other lens and loosen the large allen screw that holds the lens clamping assembly for that one lens. Move lens so that centers agree and that is it. Louis

Posted by Paul Vollmers (Member # 927) on 02-22-2013, 05:55 PM:

Use an alignment tool....?
What is that..?
And how does one find the correct lens placement?

Posted by Louis Bornwasser (Member # 3063) on 02-22-2013, 10:10 PM:

We had a long tube with a small hole in one end and a crosshairs in the other end mounted in a metal block shaped like a lens. Using a worklight in the shutter area, you could look down the tube. The goal was to have the crosshairs aligned with the center of the RP-40 test loop.

Logical, right? The center of the lens is located in the center of the picture. (Be sure to realign the lamphouse after you get the picture on the screen.) Louis

Posted by Paul Vollmers (Member # 927) on 02-23-2013, 09:23 AM:

Louis,
"loosen the large allen screw that holds the lens clamping assembly for that one lens".
We are trying to figure out which large allen screw you are describing.
And how it adjust the lens.
Sorry for the confusion?

Posted by Louis Bornwasser (Member # 3063) on 02-23-2013, 11:36 AM:

When you insert a new lens, you tighten 2 small allen screws in a clamping metal piece. The large allen screw is a pivot point for this clamping piece. I would agree that this looks unlikely, but its hole is oversize and it works. Louis

Posted by Tony Bandiera Jr (Member # 2365) on 02-23-2013, 11:36 PM:

Louis, while I agree that using the alignment tool is the 100% way of doing this, for the sake of discussion and since Paul is unlikely to have or be able to get said alignment tool, what procedure would you suggest?

I am thinking of the following:

Since the scope lens fills the screen properly (Paul: Is the illumination in Scope even across the full width of the image, i.e. the lamp is/appears to be properly aligned to the projector?) I would mark the center of the screen using RP-40.

Then, without shifting anything else, set the turret to the flat lens and adjust the flat lens holder to proper center. Now, IF the flat image cannot be centered using the adjustment of the turret, then that means the Scope lens is also offset.

If that is the case, I would then do this:

Running RP-40, and with the turret in Scope, loosen the Scope lens adjustment. Turn the adjuster in both directions, noting the offset at each extreme. Then turn the adjustment to the center of it's travel, even if the image is not yet centered on screen. (Make sure the illumination remains uniform..if not, then the lamp will need to be re-aligned as well.) Now, shift the position of the PROJECTOR Console/base to center the image on the screen.

Now, go the flat lens and center the image using the turret adjuster.

I feel the above will yield acceptable results without going thru the expense of buying the alignment tool.

Posted by Sam D. Chavez (Member # 1841) on 02-23-2013, 11:59 PM:

Before doing anything else, rotate the scope lens 180 degrees and see if the vertical center line changes. I had a pair of Schneider lenses that would move quite a lot. This made it impossible to get a common center line with flat lenses.

I finally changed out the attachments and the problems went away. This particular set of lenses were quite eccentric.

Posted by Louis Bornwasser (Member # 3063) on 02-24-2013, 07:01 AM:

Good point. Some lenses are slightly eccentric. (If very eccentric, I have seen Schneider lenses that had loose elements that, after they vibrated for a year or two, developed grooves in the side; they would not rattle. Reassembling the lens repaired everything.)

Tony's procedure would probably solve the problem as described. Louis

Posted by Paul Vollmers (Member # 927) on 02-24-2013, 07:30 PM:

Okay........here what I did so far.....!
I ran the RP-40 with the scope lens first, and found that the left and right edge alignments were pretty much where they were suppose to be equal.
Then did the same with the flat lens....auto rotated it to the flat position and found the same left and right edge alignments for the flat position to be pretty close to be equal.
However, when in the flat position the total picture is off to the left of center by 10 to 12 inches.
I also loosened the flat lens, and rotated it 180 degrees, but the picture frame on the screen was the same, off to the left.
I made no adjustments to the Turret as yet.
So at this point I don't know if the scope lens is causing the problem or the flat lens, or both.
Hope I made this clear........!

Posted by Victor Liorentas (Member # 5272) on 02-24-2013, 08:03 PM:

One thing I always do is rotate the scope lens 180 degrees and compare focus both ways...it's almost always different. One usually better than the other.
Since you may not have the alignment tool to get a perfect optical center...I would get the best scope image possible and then adjust the flat lens to agree with it.If flat focus sucks then you have more work to do but it's a good starting point.

Posted by Sam D. Chavez (Member # 1841) on 02-25-2013, 12:53 AM:

The scope lens is way more likely to be eccentric or out of round than the flat. First, any out out roundness is magnified by 2 and the lens is longer and more complex.

I did say scope in my earlier post, right?

Posted by Paul Vollmers (Member # 927) on 02-25-2013, 06:08 PM:

Yes, Sam, you did mention the scope lens.
So today I rotated the scope lens 180 degrees and looked at the picture on the screen and found that it was the same frame size and location.
It's like the very front of the flat lens needs to go a tad to the right, to center the picture on the screen to make it uniform ( equal) on both sides of the screen.
I have a 65mm scope Schneider, and a 42mm flat Isco lens.
They both have the same space upper and lower on the screen.