Strange 0.734 x 0.710 aperture plate opening size

[Tony Bandiera Jr]

Randy answered your lens protection question I believe. Unfortunately I only have experience with Strong lamphouses, someone else with more experience in the low wattage houses will have to chime in relevant to home cinema use. I'm sure there is some formula to ballpark your needed wattage relative to the throw and screen size (and gain values) to give you some tuning headroom relative to the 16fl +/- 2 foot lamberts in the corners standard.

Well, since the latter part of my cinema tech days were in home screening rooms and other small venues:

For screens up to about 15 feet wide, a 1k lamp on most lamphouses (Strong, LA Assoc, Christie after H10) is more than adequate to get the 14fl. I never used, or was a fan of, ORC products so someone more familiar with those will have to step in. Anecdotally, I have heard the ORCs had terrible light efficiency compared to the later ones I mentioned.

I did have one room with a 20 foot wide matte screen, using a 1k lamp pushed hard, that got the 14fl in scope but was about 12fl in flat. We later put in LP Assoc. with 2k and were able to run the lamp at the lower end of its range (around 1.6k) and got plenty of light, and of course the bulb lasted forever.

So, as a rough rule of thumb: (all for indoor screens, drive-ins are another ballgame.)

500w will do about 10' wide,
1k up to 15-18 feet wide,
1.6k up to 20-25 feet wide,
2k up to 35 feet wide,
3k 35-45 feet wide,
4k for 40 feet up to 60 feet wide.

And to dispel another myth that has floated around for decades:

Projection throws not exceeding 100-150 feet have no appreciable effect on the light needed. Older, slow lenses commonly used for long throws ARE less efficient, so some light loss will be noticeable.
It is the size (area) of the screen (and the image aperture) that set the required wattage for a given light output. Over 150 feet a bit of light is lost. That loss grows exponentially when distances exceed 400 feet.

[Steve Guttag]

The loss, isn't the distance, per-say, it is the lens and the maximum fastest f-stop that get you on long lenses (which you alluded to but without clarifying). You can only go to f/2 up to about 140mm. Now, with the outdoors, you can have things like fog or other air impurities that can fight you as well as the screen will need to to contend with the elements. Back in the day, there were f/1.7, 4"-diameter lenses from the major lens manufacturers (why do you think everyone went to 4" lens mounts as the Drive-In era emerged in the 40s/50s?) to get more light on screen

Light wattage versus lumens is not linear. As the wattage goes up (electrical) you are getting more and more heat as your primary manufacturing element. Furthermore, your arc is getting progressively larger, which fights you with the principle of Etendu. This is one of the big reasons 70mm is key to large-screen projection. The 70mm aperture is significantly bigger so the larger arc isn't affected as much. All things being equal, the same lamp on a 70mm system will be brighter than on a 35mm one, and progressively so, as the wattage goes up.

As for screening room lamphouses. The ORC 1000 got a LOT of use in small rooms for it could be a nice self-contained system...xenon lamp and rectifier. There was a variant with a 1600-watt external supply, as well and I saw quite a few of those and still have 1 or 2 in service.

[Ryan Gallagher]

For screens up to about 15 feet wide, a 1k lamp on most lamphouses (Strong, LA Assoc, Christie after H10) is more than adequate to get the 14fl.

Quick apology, I didn't mean to steer Adam astray by mentioning 14fL, which is the digital spec and the number sticks in my head all too easily. I've been corrected before that for film it's actually 16 plus or minus 2 fL desired in the corners specifically.

[Ryan Gallagher]

The "Academy" projection aperture for sound 35mm film is .602" x .825" or 1.37:1. You'll find that it did evolve over the years as actual practice as well as having to accommodate the realities of going from camera negative through the printing process, especially when color release prints forced the application of silver to the soundtrack area will prevent too tight an aperture. But 1.37:1 is the 35mm projection ratio, not 1.33:1. Now, for 16mm, yes, that is 1.33 or 4:3.

For sure. Hence even seeing DCPs with F137/138 and F133 as completely separate formats. Although I doubt too many cinemas bother to have a separate preset and masking and just roll with F133. But we distinguish here.

[Steve Guttag]

Since vidiots only used 4:3, unless by special request, I too will only set up for F-133 to cover all ratios in that range and do not set up, specifically, for F-137. Then again, I don't do F-210 either.

[Adam Liberman]

Quick apology, I didn't mean to steer Adam astray by mentioning 14fL, which is the digital spec and the number sticks in my head all too easily. I've been corrected before that for film it's actually 16 plus or minus 2 fL desired in the corners specifically.

I noticed that! Yes, I know 16 fL and have a good incident light meter. If the 1k lamp is too bright, the lamphouse has more than a 2:1 turndown ratio (17A - 40A). I could also switch to a 3-blade shutter, and/or possibly add aperture discs in the lenses(?).

[Ryan Gallagher]

I noticed that! Yes, I know 16 fL and have a good incident light meter. If the 1k lamp is too bright, the lamphouse has more than a 2:1 turndown ratio (17A - 40A). I could also switch to a 3-blade shutter, and/or possibly add aperture discs in the lenses(?).

Technically speaking you want a reflected light spot meter (and you meter the light coming off the screen, not the light falling on it). I've not heard of using ND filters or other insert methods to dim a lamphouse... but provided they could take the heat I assume it's a possible method.

[Adam Liberman]

Technically speaking you want a reflected light spot meter (and you meter the light coming off the screen, not the light falling on it). I've not heard of using ND filters or other insert methods to dim a lamphouse... but provided they could take the heat I assume it's a possible method.

Thanks for pointing that out. The meter can do either. I didn't mean an ND filter -- I meant something like the Schneider Premier that has an adjustable iris (f1.7 to f4), or else inserting a fixed aperture disc in the ISCO reds that I have, if that modification is possible to do. I do wonder about the heat implications of reducing the aperture on the disc or blades, since it is essentially blocking and absorbing that extra light. I don't know how the Schneider lens handles that (or doesn't) without having heat problems.

[Randy Stankey]

...or else inserting a fixed aperture disc in the ISCO reds that I have...

That would be something like a Waterhouse stop. It's an old method to stop down a camera lens, used in the days of collodion wet plate photography. (Approximately in the 1850s.)
Waterhouse stops look like washers with different sized holes in them. They are inserted into the lens at the primary nodal point. Old Waterhouse style lenses are designed to either be taken apart so that the stops can be changed or they have slots in them so that the stops can be easily swapped.

https://en.wikipedia.org/wiki/Waterhouse_stop

Modern lenses are not designed to accept Waterhouse stops. In order to add a stop to a modern lens you would have to completely disassemble it, figure out where the primary nodal point is then put the desired stop somewhere between the elements without disturbing the original arrangement before reassembling...a daunting process, indeed!

Personally, I would not disassemble any lens that I cared about using again. If I had an old lens that I wanted to experiment with, I might but a good, working ISCO red lens, I wouldn't even dream of touching.

[Adam Liberman]

Personally, I would not disassemble any lens that I cared about using again. If I had an old lens that I wanted to experiment with, I might but a good, working ISCO red lens, I wouldn't even dream of touching.

Thanks Randy, won't do it!

1) Does anyone have any suggestions for powering up these ORC 1000 lamp houses that may have not been powered up in decades? Any particular caps that tend to pop (I have a good capacitance / ESR tester and lots of electronics & audio repair/testing/modification experience)? I don't have protective gear and would prefer to pass off to someone else cleaning the reflector & lamp, checking the lamp connections, and anything else that involves exposing the lamp.

2) Would anyone happen to have the complete manual (the one in the Film-Tech downloads is missing many sections).

3) Do you know if it is ozone-free? The ORC 2500C manual says that the 2500C bulbs are, but the ORC 1000 manual doesn't mention it either way.

Thanks!

[Tony Bandiera Jr]

Quick apology, I didn't mean to steer Adam astray by mentioning 14fL, which is the digital spec and the number sticks in my head all too easily. I've been corrected before that for film it's actually 16 plus or minus 2 fL desired in the corners specifically.

That one got me too...I've been away from film for so long that the digital numbers are stuck in my head.

[Ryan Gallagher]

I don't have protective gear and would prefer to pass off to someone else cleaning the reflector & lamp, checking the lamp connections, and anything else that involves exposing the lamp.

If you are planning to be the operator of this setup, might as well add the protective lamp handling gear to your kit. All we use here is a face-shield, welder's leather apron+jacket, and some heavy welding gloves. None of which are very expensive. If you lack original packaging/case for a lamp just place it in a thick plastic rubbermaid type container while it is out of the lamphouse.

Clean the reflector and housing, look for corroded contacts. If the lamp has marks or dust on it, clean it with alcohol wipes. You are probably fine attempting to get a strike with existing electrolytic components, but if it fails to strike at all voltage ranges, or produces a very unsteady arc, then it might be time to investigate your caps etc. There is also no guarantee the lamp you have is any good, so I'd want to have a known good lamp to test with before you start tearing it apart to solve deeper problems.

After the pandemic downtime our lamps were pretty seized in the cathode holders. Yours might be too. Took more twisting and effort than any of us liked to remove or insert them. We ended up hitting the inside surface of the cathode clamp with some electricians emery cloth and now things back to normal in terms of fitment and effort required.

[Randy Stankey]

A sturdy jacket like a Carhartt brand work jacket is sufficient to protect from a xenon lamp accident. Most people around here, in Pennsyltucky, already own something like that. In some of the theaters I worked at somebody would bring in an old Carhartt jacket that they weren't using and it was kept hanging on a peg in a closet or something. When it was time to work on xenon lamps, you could just go and grab it. Besides, if you had to go outside to empty the trash or something and you needed to quickly grab a jacket, you wouldn't have to go all the way to the employee coat room to get your own.

Beside a jacket, gloves, face protection and eye protection are needed. For gloves, leather construction worker's gloves are good. Pick up a couple of pairs at Home Depot or something. For eye protection, get the fully enclosed kind of goggles with an elastic strap. You'll want something with side protection in case shrapnel ricochets around the sides. A pull-down face shied like machinists wear is also important. Goggles AND a face shield! I have been in situations where dangerous substances have been blown under my face shield and would have gotten in my eyes if I wasn't wearing my safety squints. (96% pure, lab grade sulfuric acid!) I still got burned but, if I hadn't been wearing both, I could have been in a lot worse trouble!

After all that, common sense rules. As they say, be mindful, use the brain that God gave you and you'll be all right.

[Adam Liberman]

After all that, common sense rules. As they say, be mindful, use the brain that God gave you and you'll be all right.

I'll consider doing that!!! Thanks for the detailed info.