This is topic 3d test loops in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Gordon McLeod (Member # 33) on 08-28-2001, 05:31 PM:
Looking for some 3d test loops for some old 3d overunder prints
type.380 type.383 type.387 and type.404
Also has anyone used the parralax 3d lens set. I usually use the Paramount box's but I have had a request to set up one of these wedge type systems
Posted by Jerry Chase (Member # 660) on 08-28-2001, 06:07 PM:
I used the parallel lens system on a couple of films. You "adjust" these by twisting the lens in the mount so the soundtrack edge forms a single image. That is about the extent of the adjustment you can do according to the Stereovision manual, and I don't recall any test film being used.As you probably know, you MUST use a cold dichroic mirror with this type of lens and it is good insurance to use heat absorbing glass somewhere around the snout as well. The polarizing elements in these lenses are small and take a much larger hit of heat per square inch than the mirror box types.
Plan on using a cardboard box as an extension to go outside the porthole and act as a masking agent. Flat black paint, baffles, yada yada.
I have copies of the Stereovision manuals from 1977 and 1983, but they pretty much condense down to what I just said.
As a tip, don't be concerned about the exact registration of the soundtrack as vertical registration of the images. If one image is too high it will cause eyestrain and more headaches than normal. You might find it a good idea to block off some of the seats as well, depending on the auditorium. Sitting too close and to the side can be torture. Oh yeah, test loops on 3-D single strip prints are just about worthless, IMO. The variation in how a film is shot and printed makes aligning the feature itself much more accurate than using a test loop.
Posted by Gordon McLeod (Member # 33) on 08-29-2001, 09:58 AM:
The parralax system consists of a plate that bolts on the lens with 2 rods sticking out that you then assemble various wedge prisms on off course they are coded but they don't have a book with what the codes stand for. I believe they are for various convergance angles
Posted by Jerry Chase (Member # 660) on 08-29-2001, 10:37 AM:
Got some pictures of that system, Gordon? I vaguely remember one system that had some threaded screws holding something in the lens barrel, but what you are describing is causing me to draw a blank.If something has to do with 3-D and I don't know about it, I want to know more. I don't ever recall hearing about a system with add-in prisms.
The basic registration tips I gave above would still apply. How you would reach that registration seems to be the issue.
Posted by Bill Carter (Member # 156) on 08-30-2001, 03:08 AM:
I own the same package Gordon is talking about, but also with no clue as to which prism corresponds with which convergence. Mine did have a test loop in the box with it, labeled for the film "Starchaser".