|
This topic comprises 2 pages: 1 2
|
Author
|
Topic: Adjustable pedestal for 35 flat v. scope optical centers
|
|
|
|
|
|
|
|
|
|
|
|
Tony Bandiera Jr
Film God
Posts: 3067
From: Moreland Idaho
Registered: Apr 2004
|
posted 04-16-2009 02:17 PM
quote: Stan Gunn A very common device 50 years ago,but think about it.the centre of the image of any format is always the same.
As much as I wish we lived in a perfect world, I have found that on a two-projector setup scope and flat don't always line up exactly on center...at UC Irine the difference is bad enough on my #2 projector that I have to kick (literally) the machine a few inches to re-center my scope image. No easy task with the FP-18 hanging on the back door and the double lamphouse set-up.
I attribute this problem to three things:
One, the horrid triple lens turrets on each projector. Although Kinoton makes some good stuff, I have some doubts about the accuracy of the centering of each lens hole in relation to the aperture and optical center of the film path.
Two, if the backup lens is not EXACTLY the same focal length as it's mate, there will be subtle size differences that will affect the centering of the image because of the different magnifications. Any pair of lenses used for two-projector setups must be matched within 0.5mm to be safe....I believe that the normal manufacturing tolerance on lenses can be as much as +/- 1.0mm or more.
And finally. our old friend of two-projector setups, keystone. My #2 machine is further off the center line of the screen than #1.
I was able to go into the excellent booth at UCLA, they had build custom "padds" for their Kinotons that had gearmotor driven pivot mechanisms, complete with calibrated scales so they could preset the projectors accurately without ever having to put light on the screen. They also had the single-lens mounts which, once lenses are set up correctly, hold focus during lens swaps. *sigh* I would give anything to get those mounts for my machines so I can throw those hideous turrets and aperture changers into the dumpster.
| IP: Logged
|
|
|
|
|
|
All times are Central (GMT -6:00)
|
This topic comprises 2 pages: 1 2
|
Powered by Infopop Corporation
UBB.classicTM
6.3.1.2
The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion
and agrees to release the authors from any and all liability.
|