This is topic Standard porthole height in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=001810
Posted by Mitchell Cope (Member # 32) on 01-06-2001, 09:03 PM:
What is the standard height, floor to porthole center, for the port window?I'm installing a projection booth in my basement, but I'm currently working off a portable projector. If I later get a Simplex or a Century on a base pedestal, what height should my porthole be at to minimize difficulties?
Posted by John Walsh (Member # 168) on 01-06-2001, 10:26 PM:
It varies, depending on projector and pedestal (or console) purchased. Some projector manufacturers supplied a chart that showed how large, and what height, to make the projector port window based on: the height of the lens (floor to lens center); the angle of the projector; and the focal length lens being used.
Posted by Scott Norwood (Member # 30) on 01-06-2001, 10:43 PM:
There are some basic diagrams for booth construction in the "old" SMPTE projectionist book. They're intended for a booth with Norelcos, but they shouldn't be too much different from any other booth if you have "standard" Simplex or Century bases. I know that at least the Simplex LL-2 base (which is pretty common) is (was?) available in several heights, so if you get an oddball size you may need to make adjustments in the future.I haven't seen the "new" SMPTE projectionist book, so I don't know if it contains booth diagrams or not.
Posted by Darryl Spicer (Member # 711) on 01-06-2001, 11:08 PM:
By not knowing what type of equipment you are going to use makes the calculations a bit dificult. I would say that the bottom of the port should be three feet from the floor and the top should be five feet from the floor. Make the port two feet wide. Remember to angle the glass so that any back reflection from the projected image is projected torwards the floor and not back into the lens.
Posted by John Eickhof (Member # 323) on 01-06-2001, 11:27 PM:
The original standard set by manufacturers in the 1920 is centerline of picture out from projector at 0 degrees tilt (level) is 47 inches. The port size due to codes existing at the time was a maximum of 144
square inches (12" x 12") That code is now obsolete and has been discarded in most areas. However, today's equipment still bases 47 inches as standard height for a 0 degree tilt. Whether its a console or a conventional base. I hope this helps! Generally in home screening room booths, projection ports of 12" high x 14" wide are the norm, and are easy to frame between studs. The view or operators ports are generally set at 64" center line of port from floor.
Good luck! If you need any other info, email me! I have built many screening rooms through the years! John http://www.nteequip.com
Posted by Paul G. Thompson (Member # 655) on 01-07-2001, 12:48 AM:
In addition to what John said, you have to be very careful with the short-throw big screen houses. We have three of such, and because of the projection angle, the bottom sill of the projection porthole is about 33 inches off the floor. Schneider Optics has a beautiful lense calculating program. It'll cite the size of the image on the porthole glass, but it does not cite how far off the floor the bottom sill should be. You have to figure that out yourself. 
Posted by John Eickhof (Member # 323) on 01-07-2001, 05:20 PM:
Paul is correct in that short focus lenses will require a larger port! This comes into play on any short throw with a wide screen!
You can easily figure the height of the port by doing a scale drawing with the projection line at 47" O.C. (level) Then measure distance from port (or wall) to the pivot point of the pedistal or console, swing a line out from this pivot point at the estimated up or down angle (in degrees off level) Then scale this line from floor at proposed port position and you will have your port located! Good luck!!!
Posted by Gordon McLeod (Member # 33) on 01-07-2001, 08:31 PM:
yes autocad makes that even simmpler