This is topic Why single lens holder? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Demetris Thoupis (Member # 833) on 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
Posted by Jon Bartow (Member # 241) on 11-11-2002, 06:53 AM:
one word:
Money(or more correctly, the lack thereof)
Posted by Daryl C. W. O'Shea (Member # 1303) on 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.
Posted by Stephen Furley (Member # 1277) on 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.
Posted by Steve Guttag (Member # 268) on 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!"
Posted by Scott Norwood (Member # 30) on 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.
Posted by John Hawkinson (Member # 1135) on 11-11-2002, 08:08 AM:
What's a "PC adapter?"--jhawk
Posted by John Pytlak (Member # 331) on 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
Posted by Daryl C. W. O'Shea (Member # 1303) on 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! 
Posted by John Pytlak (Member # 331) on 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
------------------
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
Posted by John Hawkinson (Member # 1135) on 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
Posted by Steve Kraus (Member # 476) on 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.
Posted by Leo Enticknap (Member # 534) on 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.
Posted by Steve Guttag (Member # 268) on 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!"
Posted by Scott Norwood (Member # 30) on 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?
Posted by Steve Guttag (Member # 268) on 11-12-2002, 03:44 PM:
Yes, the 4" diameter lenses were generally faster. For Drive-Ins where long focal lengths are often employed, the larger lenses (and scope adapters) allowed for brighter pictures. On the other end of the scale, the 4" diameter lenses allow for very short focal lengths without vignetting.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Gordon McLeod (Member # 33) on 11-12-2002, 04:17 PM:
I didn't think they made any 4" diameter lens shorter than 4" (except for some of the newer 70mm lens
Posted by Per Hauberg (Member # 529) on 11-13-2002, 06:56 PM:
"Why single instead of turret ?"For a start, try disassempling a cinemec turret and put it together again....
Second: Nothing's better than a big, solid focus-handle with plenty of space around it for fat fingers. -Once again, ladies & gents: The Fabulous Philips DP70 !! (fanfare here)
Third: If You are running repertoire (or dogme-95), You often need the 1,37 - And again the Cinemec turret will steal Your time and spoil Your mild temper, before You're ready after chancing one of the three...
Single lens holder for me again next time, -thank You !
Per
Posted by Steve Guttag (Member # 268) on 11-13-2002, 09:47 PM:
4" diameter (101.6mm) has always been at the opposite ends on the focal length scales. The old ISCO "Spezial" lenses were 101.6mm diameter and went down to 31.3mm for 35mm only. Then there was the Kiptikon series of 101.6mm diameter lenses. The B&L Super-Cinephores and Kollmorgan lenses were only of the longer variety, that I am aware.Steve
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"Old projectionists never die, they just changeover!"