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Topic: Why single lens holder?

Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001

posted 11-11-2002 06:51 AM

Hi again.
One more question. Why do cinemas install projectors with single lens holder when there are so many options of two or even three lens turrets? I am curious
Demetris Thoupis

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Jon Bartow
Master Film Handler

Posts: 287
From: Massachusetts
Registered: Nov 1999

posted 11-11-2002 06:53 AM

one word:
Money

(or more correctly, the lack thereof)

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Daryl C. W. O'Shea
Film God

Posts: 3977
From: Midland Ontario Canada (where Panavision & IMAX lenses come from)
Registered: Jun 2002

posted 11-11-2002 06:54 AM

Some reasons:

1. Turrets cost more money.
2. Lenses are easy to change by hand.
3. Turrets are 'harder on' heavier/longer lenses.
4. Some non-integrated scope lenses block the flat image in some turrets.

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Stephen Furley
Film God

Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002

posted 11-11-2002 07:20 AM

The Kinoton interchangable single lens holders are quite popular here. I can change lenses with them in about three seconds, with the new lens always being correctly focussed. They have the great advantage over turrets that you can have as many lenses as you need, and are not limited to the two or three that you can put in a turret.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 11-11-2002 07:50 AM

Lens turrets are only really popular for multiplexes. They act as lens holder as well as lens cabinet. While there is a great feeling of flexibility with them since you can adjust for perfect center on each format, they rarely keep their adjustments.

On American machines, single lens holders got a bad rap for being out of round so no two insertions put the picture on the screen in the same place. This really isn't the case anymore. Furthermore, with PC adapters (used instead of lens adapters) the single lens holder can have all of the flexibility of the turret but with an infinate number of formats available.

Given the choice, I'll go for single lens holder EVERY time. However, it depends on the booth personel too...Scope lenses were heavily abused by incompetent operators in the single-lens holder days. Funny, we don't have this sort of problem in the screening room type booths.

Steve

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"Old projectionists never die, they just changeover!"

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 11-11-2002 08:02 AM

Turrets can be nice if you only have two formats to deal with, but they would be a pain for dealing with additional formats. I doubt that anyone will ever make a four-lens turret.

I agree that the Kinoton lens collars are great. They seem to position the lens much more precisely than Simplex or Century collars.

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John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 11-11-2002 08:08 AM

What's a "PC adapter?"

--jhawk

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-11-2002 08:36 AM

In most cases, with the general availability of both "flat" and "scope" trailers, it is possible to make up a show having only one format, and requiring no lens/aperture change during the show. When you have a mix of formats in an automated situation, a turret and aperture changer are needed, along with automated screen masking.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

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Daryl C. W. O'Shea
Film God

Posts: 3977
From: Midland Ontario Canada (where Panavision & IMAX lenses come from)
Registered: Jun 2002

posted 11-11-2002 08:40 AM

I used to do lens changes while rolling all the time. Much more fun than you can have with turrets!

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-11-2002 08:42 AM

JHawk asked: "What's a "PC adapter?"

It's not a "Politically Correct" adapter, but rather one to achieve perspective correction or keystone correction:
here Schneider PC Keystone Corrector

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John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 11-11-2002 08:42 AM

"Ladies and gentlemen, the following trailer is in Cinemascope. Please put on your Cinemascope glasses to fully appreciate the experience."

--jhawk

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 11-11-2002 11:02 PM

What did they do about lens changes on 76mm (small) barrel machines or did those designs all predate widescreen? I'm referring to the ability to pop in a lens in focus. It's not that you can't put a ring on directly on a lens instead of on a 4" adaptor but that principle is based on snugging that ring against a lens mount that extends out the front of the machine. On the older machines you only have the casting to butt up against. I've done prefocused lens changes on those machines by using an extension tube and an external lens clamp using the front of the machine as a temporary reference but it was hardly the ideal.

It's a shame cinema projection lenses still use such a primitive mount instead of something like a bayonet mount.

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Leo Enticknap
Film God

Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000

posted 11-12-2002 05:43 AM

Turrets would be useless on some projectors (e.g. a DP-70) anyway, because you need to stop the motor in order to change the aperture plate.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 11-12-2002 07:42 AM

Steve...those projectors predate the widespread use of formats other than the Academy ratio. Remember E-7s and Supers had front shutters even! The Century C had a large lens mount at the end of production and the H and SA all had large lens mounts. Simplex went to the large lens mount with the X-L in 1949...predating CinemaScope by several years.

Steve

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"Old projectionists never die, they just changeover!"

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 11-12-2002 08:07 AM

What about those lenses where the lens itself is 4" in diameter and doesn't need a collar at all? Are they supposed to give more light on the screen or something?

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