Film-Tech Forum ARCHIVE: Interchangeable Lenses???

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Posted by Barry Floyd (Member # 385) on 09-17-2002, 11:14 AM:

Here's a question I thought of over the weekend. I've got one Simplex XL, and the lenses that I've for it came from an old drive-in. I've got a total of four lenses (2 scope & 2 flat). All of the lenses have this big bushing/adapter thing on them that are made to slide into the lens barrell of an XL. Since our theatre will have a different throw and screen, I figured I'll have to buy another set of lenses anyway. Our new theatre will be a twin screen drive-in, and I currently have 1 XL and 4 BX-60's. Can I use the same lenses on a Brenkert that I would use on the XL. My thoughts are to open with one booth running the XL, and the other booth running the Brenkert. As finances allow, I'd like to replace the Brenkert in the booth with another XL.

Are the lenses interchangable with the exception of the adapter/bushing collar? That would save me from having to buy another set of lenses one or two years down the line.

------------------
Barry Floyd
Floyd Entertainment Group
Lebanon, Tennessee

Stardust Drive-In Theatre
Watertown, Tennessee

Posted by Aaron Sisemore (Member # 145) on 09-17-2002, 11:33 AM:

Yes, if you remove the collar the lenses will fit in your Brenkert, or any other machine that takes standard 70.6mm diameter lenses.

However, you might want to think of looking at these lenses very carefully and ask yourself if its worth it to use them for your particular application. The older (40's-70's) Kollmorgen and B&L lenses are far fom the optimum to achieve maximum light efficiency (important in a D/I), and a good majority of the B&L anamorphics have discolored to a yellow tint, making them that much more useless.

-Aaron

Posted by John Pytlak (Member # 331) on 09-17-2002, 11:58 AM:

Standard SMPTE 243M specifies 35-mm and 70-mm Projection Lenses and Mounts. "Standard" lenses have a barrel diameter of 70.66mm (2.782 inches), and the nominal clamping area of the barrel is from 101.6mm to 152.4mm (4.00 to 6.00 inches) from the film plane. The minimum distance between the film plane and the back of the lens is 30.5mm (1.20 inches).

"Large" lenses have a barrel diameter of 101.35mm (3.990 inches).

------------------
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 Barry Floyd (Member # 385) on 09-17-2002, 12:34 PM:

The existing lenses I have are indeed the old Bausch & Lomb lenses. They were in use up until the time the drive-in closed in 1998. The scope lens does have a very slight "yellow" tint to it, but not extremely dark. I had not planned to use the old lenses, but purchase new ones at the time when our place opens in April.

So if I understand correctly, whatever new lenses I purchase will be able to interchange between the two machines with the exception of the collar?

------------------
Barry Floyd
Floyd Entertainment Group
Lebanon, Tennessee

Stardust Drive-In Theatre
Watertown, Tennessee

Posted by John Pytlak (Member # 331) on 09-17-2002, 12:49 PM:

Do you have the correct lens focal lengths for the throws and screen sizes you are planning on? Even in a drive-in, you need to "Care About Composition":
http://www.kodak.com/US/en/motion/newsletters/pytlak/spring2001.shtml

Generally, you should size your screen for a 2.39:1 aspect ratio, and use lenses that will give a common height image for "scope" and "flat". Cropping the image or using outdated lenses just cuts down on the little light you have to fill those big screens.

Optimum viewing distances in a drive-in are usually further back, so customers can see the entire screen through their vehicle windshields.

Posted by Robert E. Allen (Member # 1351) on 09-17-2002, 01:57 PM:

If your Brenkert machines are in good shape don't be too quick to dump them Barry. Those things are built like a tank and if properly maintained will probably outlast you. The one advantage of changing to Simplex is that the Simplex is still manufactured while Brenkert is not. But check with the parts houses (LaVezzi, Wolk) first to see if they are still making parts for the Brenkert before you make your decision.

Bob
The Old Showman

Posted by Aaron Sisemore (Member # 145) on 09-17-2002, 05:05 PM:

>>So if I understand correctly, whatever new lenses I purchase will be able to interchange between the two machines with the exception of the collar?<<

Yes, the new lenses will physically fit both projectors (Simplex XL requiring the adapter collar of course).

Unless both applications use the same focal length lenses, they will not be functionally interchangeable.

-Aaron