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Author Topic: How to set up scope focus
Mark L Barton
Jedi Master Film Handler

Posts: 621
From: Bristol, South Glos, England
Registered: Mar 2009


 - posted May 31, 2017 07:12 AM      Profile for Mark L Barton     Send New Private Message       Edit/Delete Post 
Hi all. I am projecting onto a large 15ft screen with an Elf 16MM with a scope lens in dedicated elf bracket, yet I cannot get a sharp picture. On much smaller screens and using a freestanding scope holder I can get a razor sharp image, but not on this long throw.
Your advice please.

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007


 - posted May 31, 2017 02:02 PM      Profile for Maurice Leakey   Email Maurice Leakey   Send New Private Message       Edit/Delete Post 
Mark
1) Set the anamorphic to the approximate throw on its scale
2) Without the anamorphic in position run a film and focus the normal backing lens
3) Swing anamorphic into position
4) Continue running the film and then fine trim picture with the anamorphic
5) Finish with a final "tweak" with the backing lens

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Maurice

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Mitchell Dvoskin
Expert Film Handler

Posts: 128
From: West Milford, NJ
Registered: Jun 2008


 - posted May 31, 2017 02:10 PM      Profile for Mitchell Dvoskin   Email Mitchell Dvoskin   Send New Private Message       Edit/Delete Post 
This is what I do:

On the scope lens, there are marking indicating either meters or feet, depending upon the scope lenses vintage and origin.

1. Loosen the tiny lock screws so that you can turn the outer ring of the scope lens, lining it up about where the markings indicate the distance between the projector and the screen.

2. Run a film with high contract end titles (white letters against a dark background) with just the prime lens without the scope attachment.

3. Focus the prime lens, tape down the focus knob so it does not move.

4. Place the scope lens in front of the prime lens. There should be no vertical ghosting above or below the letters. If there is, you can fine tune by re-focusing the prime lens with the scope lens in place.

5. Turn the scope lens's focusing ring until there is no horizontal ghosting to the left or right of the letters.

6. Done. Tighten the tiny lock down screws so the scope lens focus does not shift.

NOTE: I have seen very few razor sharp 16mm scope films. Many are slightly off from the lab. However, any softness should be very minor.

NOTE: There are a lot of second hand scope lenses out there that have had some of the internal elements knocked out of alignment, and will never focus correctly. Since at short distances you can focus correctly, I don't think that this is your problem.

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Clyde Miles
Expert Film Handler

Posts: 205
From: Bromsgrove, UK
Registered: Nov 2013


 - posted May 31, 2017 04:59 PM      Profile for Clyde Miles     Send New Private Message       Edit/Delete Post 
ok, what about a scope lens that screws into a primary lens, how does that work?

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Steven J Kirk
Jedi Master Film Handler

Posts: 873
From: Southern England
Registered: Apr 2008


 - posted May 31, 2017 08:47 PM      Profile for Steven J Kirk   Email Steven J Kirk   Send New Private Message       Edit/Delete Post 
Best to break out the tape measure and actually measure the distance. Then set that on the scope lens. Then you know one is good and it is just the normal focussing on the back lens.

--------------------
VistaVision
Motion Picture High-Fidelity

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Mitchell Dvoskin
Expert Film Handler

Posts: 128
From: West Milford, NJ
Registered: Jun 2008


 - posted June 05, 2017 03:29 PM      Profile for Mitchell Dvoskin   Email Mitchell Dvoskin   Send New Private Message       Edit/Delete Post 
> ok, what about a scope lens that screws into a primary lens, how does that work?

Same concept. Vertical ghosting is adjusted by focusing the prime lens, horizontal ghosting is adjusted by focusing the scope attachment. Does not matter if it is screwed or a separate bracket. The distance marking on the scope attachment get you close.

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007


 - posted June 06, 2017 02:41 AM      Profile for Maurice Leakey   Email Maurice Leakey   Send New Private Message       Edit/Delete Post 
I should point out that ghosting is caused by the intermittent and the shutter being out of phase with one another. It has nothing to do with focus.

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Maurice

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