|
This topic comprises 2 pages: 1 2
|
Author
|
Topic: Focus problem with scope features only.
|
|
|
|
|
Brad Miller
Administrator
![](http://www.film-tech.com/ubbmembers/02a.jpg)
Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99
|
posted 12-30-2004 10:49 PM
1. Thread the loop of PA35 test film into the projector, making sure the loop does not hang in front of the lens. Depending on the particular anamorphic you are using, you may have a small thumbscrew, set screw, or a ring collar at the front of the lens. Loosen the locking mechanism so that you can freely turn the outer focusing (or more precisely: the astigmatism adjustment) ring (labeled with measurements, commonly from 20 feet to 150 feet). Note the current setting before changing it for reference.
2. Turn the focusing ring all the way down as low as you can go (about 20 feet). If you are in a short throw theater, such as a screening room, you might be better off turning it to it's infinite setting (typically 150 feet).
3. Turn the projector and lamp on. Notice the image will be incredibly blurry. Use the projector's focus control to focus the horizontal lines on screen to be as sharp as possible. Ignore all vertical lines. Once you get the projector's focus set in this manner, do NOT touch it again for the rest of this process.
4. CAREFULLY and slowly, turn the focusing ring on the anamorphic lens itself. Continue to turn it until the vertical lines converge and become as sharp as possible. Again, ignore all horizontal lines.
5. Now, without bumping the focus setting on the anamorphic, tighten the locking mechanism.
Your lens is now optimized for your projection throw. Because this method is accomplished by focusing through the lens as opposed to counting the distance from lens to screen (commonly by counting ceiling tiles), your end result will be a sharper image.
If you don't have an RP40/PA35 loop of film, you can use a scope green band from a trailer to get pretty close (but not *quite* as accurate as using a real test loop). Thread the green band loop 2 perfs out of frame and use that horizontal frame line to set your focus...then re-center the framing and adjust your astigmatism adjustment on the anamorphic until the letters in the text are as sharp as possible.
| 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.
|