Film-Tech Forum ARCHIVE: Stereovision 3D lens question

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Posted by Ed Inman (Member # 2583) on 10-19-2015, 12:37 PM:

Can anyone confirm whether this lens attachment pictured is designed for side-by-side 3D films in conjunction with a prime lens and anamorphic attachment? Or is it for the upper/lower type 3D films? thank you, Ed

Posted by Steve Guttag (Member # 268) on 10-20-2015, 06:44 AM:

That appears to be an over/under version of their lens from the very early 80s. Note, their side-by-side lens looks pretty much the same though. By the mid-80s they had gone to a mirror box type attachment instead of being in the prime lens business...including for side-by-side.

Posted by Frank Bolkovac (Member # 6201) on 10-20-2015, 11:30 AM:

Gave a friend of mine one of those who collects 3d films Side by side and over and under. Told him to try side by side with prism adjusted in the side by side position and over and under in that position. Told me it works with some adjustment. Hope this helps....Don't forget you need a silver (Aluminum) screen.

Posted by Ed Inman (Member # 2583) on 10-20-2015, 01:01 PM:

Thanks for the feedback. I'm trying to find one that will project a side-by-side 3D film with a scope attachment. I guess in theory it could work either way. I know I need a silver screen and polarized glasses but I'm still in the dark about things like focal length and getting one to properly fit the screen. My normal prime lens that I use with an ISCO scope attachment is 6 inches or about 150mm with a throw of 50 feet. If I can make it work this will just be a free screening for some friends, so it doesn't have to be perfect but I'd like it to look reasonably good. Any additional general advice as to what model Stereovision lens would best work would be much appreciated. As a last resort I assume I could cut an aperture plate to project just one side of the film in non-3D format?

Posted by Frank Bolkovac (Member # 6201) on 10-21-2015, 11:05 AM:

I wouldn't use a scope attachment as it would distort the image. 3D prints are usually flat. The lens you have is probable fixed for a certain size. Try using a Magna-com lens attachment which may screw on the front to increase the size of your picture. Some are adjustable (like a zoom lens).Seen a couple on E-bay some time a go. If your picture is too small, the magna_com will increase the size. If the picture is too big, turn the magnacom backwards and it will decrease the size.This will depend on the actual size of the fixed rate of your 3D lens. The black collar on your 3D lens would have to be removed (should just screw off) and the magna-com directly coupled to let as much light through without (stopping it down). Hope this is somewhat helpful....

Posted by Stephan Shelley (Member # 8587) on 10-21-2015, 05:57 PM:

Side by side is used for 1:37 to 1 prints. As one is squeezing the image to half the frame, the normal 2 to 1 scope lens spreads it back out. You have to have a focusing type scope attachment. The prism type attachments will not work. Normaly you would put the theatre's scope attachment on the front of Sterovision's split lens.

The mirror boxes are better.

Posted by Ed Inman (Member # 2583) on 10-21-2015, 06:37 PM:

Thank you--do you know what brands of a scope attachment are the "focusing" types? All I currently have is an ISCO. I'm also being given a "Siriuscope" 3D lens (see picture). Not sure it will work but worth a try I guess. Anyone heard of those? A Stereovision copycat perhaps?

Also, Frank, yes I am aware under/over 3D films are flat, but the less-common side-by-side ones require the scope attachment I am told.

Posted by Stephan Shelley (Member # 8587) on 10-21-2015, 07:13 PM:

The focusing ones are the ones that a real lenses with the distance adjustment on the front. Look in the front of the one you have. If you see a prism it is not. ISCO Synder B & L and Kollmorgan all made the type I am talking about.

Stephan

Posted by Ed Inman (Member # 2583) on 10-21-2015, 07:27 PM:

Thanks for the clarification. Yes my ISCO attachment has this. I believe it is actually called the astigmatism adjustment.

Posted by Don Furr (Member # 1469) on 10-21-2015, 11:26 PM:

Ed, before Technicolor make their new 3D lens several years ago, that Sirius Lens you have (in the last picture) was the best lens available.
The focal length was available in 1/4 inch increments beginning, I believe with 1:75. The Sirius lens has a single eye focus adjustment as well as another adjustment to change the spacing as required depending on the 3D movie being projected. In order to set up the lens you'll need a test film for the spacing required. It's a tedious process requiring patience.
I have the manual for the Sirius II lens if you need a copy. I can also send you a copy of all the the over/under 3D titles with the spacing numbers for each title.
I also have a spare 3 inch focal length lens if that would fit your screen better.

Posted by Ed Inman (Member # 2583) on 10-22-2015, 10:50 AM:

Thanks Don, a manual would be very helpful. I emailed you my contact info. I'm not sure what focal length the one being sent is--I'll just have to try it and see. Should be here in the next day or two. It will be next summer before I actually try to use it with an audience so I have plenty of time to experiment. thanks again, Ed

Posted by Gordon McLeod (Member # 33) on 10-22-2015, 11:37 AM:

The original sterovision lens had no adjustment for the spacing between the left eye right eye on a rather crude convergance
The Sirus allows for both the only issue as one has to keep taking the anamorphic off to get at the screws
the schnieder technicolor lens put them at the back which is easier
I often use the paramount mirror box with a small compact anamorphic