Film-Tech Forum ARCHIVE: Has any "standard" height been established for projector port position?.

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Posted by Frank Angel (Member # 248) on 12-20-2017, 01:13 PM:

I have searched around but haven't found anything specific, but I have to assume there is some sort of standard for the position for the projector port windows relative to the floor, no? Otherwise it would be a mess when projection heads or complete projectors from different manufacturers are swapped out. Surely when a projector is placed on a pedestal from any one of a variety of manufacturers, the lens height relative to the floor is the same. If not, it would just be mayhem. Then again I have learned over the years that making assumptions can bite you quite seriously in the butt.

Reason I ask, in these two screening rooms I am involved with, both booths have ports that are simply too high I were to put in a 35mm/70mm system. I am not too surprised in that the port glass looks like window plate glass -- nice green edge showing -- and the glass closest to the lens is perpendicular to it, not slanted. The ports looks like they were place so a HUMAN can see comfortably out of them, not a projector beam projecting an image.

Remembering back a few decades when we installed the Simplexes in the large theatre, the booth seemed to be built to whatever specs there were at the time -- it was a nitrate compliant booth -- auto-mechanical shutters on the ports and mechanism that would slam the doors closed if a fire melted the safety links (creating a nice projectionist flambé), but when I set the projectors in place and fired them up, much to my surprise, they were not high enough to clear the port. The reason for my surprise was that the booth seemed to be vintage and met all the specs. I had to raise the pedestals about a foot to get the beam out the ports. Admittedly, some of that was because of the height of the booth (5 stories above the orchestra floor) so the very steep angle plus the fact that the booth wall the port was cut through was a double-cinderblock and brick structure within the hang-ceiling structure made it about a foot and a half thick, but even given all that, if there were some standard placement, the beam should have at least not hit the wall instead of out the port...again, I would assume.

Is there some standard position? Probably something only important for film booths -- film projectors and their pedestals and consoles being so massive -- video projectors can be easily placed pretty much wherever the port happens to be given their much smaller footprint.

Posted by Steve Guttag (Member # 268) on 12-20-2017, 02:00 PM:

Film projectors, pointing straight/level have a lens height of 47-48" from just about any manufacturer.

That height has to be adjusted based on the down angle. But in order to calculate that you have to know what your pivot point is. On a console it is down by the foot. On a pedestal it up up at the knuckle. So in addition to tilting, you are also lowering and moving forward as the image goes down.

You also have to allow for where the image is on the theatre-side of the port more than the booth side since the image is growing as it goes through the port.

In DCinema, there is no standard as there are all sorts of pedestals, tables and what not. Plus you have so many things affecting the lens height including the pedestal feet, the projector feet and any tilting mechanism a pedestal/shelf may have.

Posted by Dave Macaulay (Member # 813) on 12-25-2017, 08:49 AM:

Generally, if you put a Barco projector on the Barco pedestal or a Christie on a Christie pedestal, the lens height will be compatible with a normal 35mm booth port. The lens will be low with the levelers in all the way... since it's rather difficult to lower from there if the port is low. Barco projector feet screw out a LONG way, I don't like them too far out as the unit gets a bit shaky. Pedestal feet will lift about 6" as well. If you use the wheels you lose the pedestal height adjustment, but wheels are rarely used now.
We have installed digital systems in a lot of very old cinemas with the tiny nitrate era ports, and haven't had to get out the jackhammer yet. A few projectors are sitting on additional risers, but the 35mm projectors were on them previously... stadium rooms where they wanted to get the projection beam above back row heads.

Posted by Steve Guttag (Member # 268) on 12-25-2017, 09:22 AM:

I have found, particularly the older one, the Christie pedestal to be rather tall. The current one not only is right for film port height, it has a built in riser (the feet section telescops).

Posted by Charles A. Petty (Member # 3458) on 02-03-2018, 05:55 PM:

From the booklet published by Motiograph called "A Model Projection Room" it appears that 48" was the recommended height from the floor to the optical center of the 35mm projector and the projection ports should be at least 10" x 10".

Posted by Steve Kraus (Member # 476) on 02-03-2018, 11:38 PM:

This might be of some historic interest. It's from Century by way of the old NATO / SMPTE Presentation Manual.