With Technicolor Schneider 3D lens, how to determine prime lens focal length?

[Gary A. Hoselton]

I don't have a Technicolor Schneider 3D lens yet, but am interested in experimenting with one. From photographs, I don't see focal length of prime lens labeled on outside. What was available, and how are they identified? Now that that era is over, has anyone written or leaked an explanatory document?

[John Eickhof]

it depends on several variables...is the 3D single frame side by side or over and under? either way, any standard 2 25/32dia lens will fit the adaptor but if its side by side, some prints require an anamorphic adaptor, if over and under, you would end up with a slightly under 2:1 picture. if two machine 3D you would use a lens and aperture plate for 1.37: ratio. if the back-up lens has 'split elements' then you may have a difficult time finding a focal length other than what you have because the split lenses were made to order...I prefer the stereovision set up because it uses standard back-up lenses...have fun!

[Randy Stankey]

You can estimate the focal length of a lens by pointing it at a bright source of light from a distance (such as a bright, sunlit window across the room) and focusing the image on a white card. Then just measure the distance from the card to the center (nodal) point of the lens.

This won't be super accurate. It will probably be imprecise by a few millimeters in either direction but, since we know that most lenses are made to even focal lengths (in steps of 5 mm, for instance) you can make an educated guess of what the actual focal length is. Then, you can look up the manufacturer's specs to see what focal length your lens should be.

An anamorphic lens in front of the prime shouldn't interfere with this experiment too much as long as it is focused relative to the prime. Even if it's not you should still be able to just ignore the anamorphic as long as you can determine which direction the anamorphic lens goes. Just ignore any soft focus along the anamorphic axis.

Like I said, it won't be perfect but, if you are careful, you should be able to come up with a close estimate.

[Gary A. Hoselton]

My present interest is screening over/under 3-D film, which I've had some of on the shelf for years just sitting there. I have three Paramount kits and a Sirius O/U lens, which makes me curious about the Technicolor Schneider lens which appears to consist of a splitter and prime lens screwed together, and my only question so far is where focal length of the prime lens is labeled.

Randy, neat way to estimate focal length. I just tried it with a 2" 16mm lens, and my rough measurement is within 1/4" of 2" from sharp image on paper to center of optics in lens. Thanks.

[Randy Stankey]

...my rough measurement is within 1/4" of 2" from sharp image on paper to center of optics in lens.

Happy to help!

The tough part is finding the center (nodal) point of the lens.
Some lenses actually have it marked on them. For photography lenses (versus projection lenses) you can sometimes find the nodal point by looking for the aperture or iris. The stops, be they Waterhouse stops, dial stops or iris are located at the nodal point.

I have a view camera that has the nodal point marked on the lens because the photographer sometimes needs to know the actual focal distance to calculate exposures and stuff. I have another, old camera that I don't use which has a dial stop and I have a very old lens that belongs to some unknown (to me) camera which uses Waterhouse stops. They look like brass washers, basically.

For my more modern lenses and cameras, they usually don't have the nodal point marked on them. Maybe only one or two of them do. Hard to remember which unless I go look.
Anyhow, in those cases, it's pretty much an educated guess.

All-in-all, being 1/4" off on a 2" lens isn't too bad at all.

[Marcel Birgelen]

I have no experience with those kind of 3D lenses, but I can't really remember any projector lens that had its NPP marked on the outside. Then again, most lenses don't mark their NPP on the lens barrel. A photographer I know once told me you can easily find it by using a laser pointer. A little Googling yielded this article on how it's done.

PS: Be careful when pointing laser pointers at stuff like lenses, since internal reflections inside the lens can quickly reflect beams in all kinds of unexpected directions. While most laser pointers are pretty harmless for short exposures, some of those "made-in-China" models seem to pack more punch than you might have bargained for.

[Mark Gulbrandsen]

Note that the T-3D system was merely a drastically improved Stereovision system, Technicolor bout the rights from Steve's daughter. It used circular polarization instead of linear and frame to frame C/L was slightly larger than Stereovision. I .Did about 20 of those installs back when it was the fill in gap for theaters that did not yet go digital. We had to go to the theater in question and do a site survey. Then, send it in to Technicolor so they could see if it would work and the conditions were acceptable, amost always we had to also install a new lamphouse or a reflector modification with in the existing one. Then they sent us back the lens specs and or the lenses. Usually the theater was shipped the lenses directly, but I also had the full technicians kit in case there were issues. . Also, Panavision has a 3-D projection system that can run on any screen surface be it silver or white. Its similar to Dolby 3-D, in that it's a comb filter system but it's way more efficient that Dolby. Dolby causes 80% light loss...

[Gordon McLeod]

The technicolour lens were purchased from Schnieder and were the standard Isco/schnieder 3d lens. They only can converge over under prints and in all case were used with variable magnifiers

[Frank Cox]

It's my understanding that those lenses were only in use for a very short period of time before they were obsoleted by the digital change-over. What happened to them after that? Abandoned at the theatres that were using them, or they were supposed to be returned to Technicolor?

I imagine that Technicolor paid a significant amount for them at the time they were purchased. I wonder if they got their money back out of them before they were old news.

[Marcel Birgelen]

It's my understanding that those lenses were only in use for a very short period of time before they were obsoleted by the digital change-over. What happened to them after that? Abandoned at the theatres that were using them, or they were supposed to be returned to Technicolor?

I imagine that Technicolor paid a significant amount for them at the time they were purchased. I wonder if they got their money back out of them before they were old news.

You quite often see that you're legally required to return certain equipment, but then it gets abandoned by those who "loaned" or "leased" it to you. Since those lenses are hardly copyright-sensitive material, it wouldn't even make sense for them to ask them back, as they probably have close to zero resale value for them and it would only cost them for the shipping and stocking and possibly recycling of those lenses.

[Gary A. Hoselton]

Gordon, was this lens a Schneider product before Technicolor came along? Was there only one focal length of the prime lens portion, or perhaps three focal lengths were available (as in picture of the installers kit), and a variable magnifier was screwed on to accommodate the theatre? Was the focal length of the prime lens labeled on it, or how did you folks keep track of or make up what was needed? Thanks for info, for this is history which shouldn't be lost.

[Steve Guttag]

It was an ISCO product before Technicolor came along. Schneider had reacquired ISCO towards the end of film...there is a long story on the whole ISCO/Schneider thing. That said, the Technicolor version was not simply a direct off-the-shelf version, they merely used the existing ISCO lens as a starting point and then combined it with magnifiers, added some features to get the alignment and eye-to-eye focus better. So it was a new product based on existing technologies. It is telling that, in the end, the ISCO line was the dominate lens line that Schneider continued. Only some aspects of their own cinema lenses did they continue (variable primes, for instance, that ISCO never had).

[Stefan Scholz]

Yes, it was the old Iscovision 3D lenses they used, from that point, you can find the limited number of focal lengthes in the Isco catalog of the time. Unfortunately not at hand now. It wasn't a large number of focals. So you had to adjust the screen masking in most cases.
The system worked, like most of these over under quite okish, but only on small screens. And, the price Technicolor asked was multiples of what the things cost at Isco, when the company was still Isco.

[Mark Gulbrandsen]

The technicolour lens were purchased from Schnieder and were the standard Isco/schnieder 3d lens.

That's not what I was told in training at Technicolor. I was told the center to center distance on the frames was increased slightly to try to up the resolution and light output. Was also told that Technicolor bought the rights to the Stereo Vision process and that this is based on that with minor modifications. Since these systems were so short lived I did not get to try running a Stereo Vision print on a Schneider lens.

[Gordon McLeod]

I have run many old over under titles on the tech lens.