This is topic Help with Specs for New Theatre 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=004595

---

Posted by Manny Knowles (Member # 1171) on 02-24-2003, 10:42 PM:
 
Right now, I need verification that I'm calculating the estimated Xenon requirements correctly.

I have plans here depicting screens that will be 20, 30, 40 and 60 feet wide.

20'W x 10'H = 200 sq ft x 5W = 1000W Xenon
30'W x 15'H = 450 sq ft x 5W = 2750W Xenon
40'W x 20'H = 800 sq ft x 5W = 4000W Xenon
60'W x 30'H = 1800 sq ft x 5W = 9000W Xenon

Am I doing this right?
How does throw distance impact these calculations?
 

---

Posted by Daryl C. W. O'Shea (Member # 1303) on 02-24-2003, 10:56 PM:
 
2:1 screens! Who's idea was that?

Your 9000W lamp isn't going to happen.
 

---

Posted by Paul G. Thompson (Member # 655) on 02-24-2003, 11:30 PM:
 
Better adjust your screen sizes so you can run the full 1:85 and 2:35 ratios. We used movable masking on top and bottom of some of our screens because we wanted to maintain the width. It worked out excellent for us. But with a 40 amd 60 foot width, that could be a horse of a different color. The vertical throw of the masking might be just too much unless you have stadium seating. My .02 cents worth....

I could be wrong, but the throw calculation added for Xenon power in an indoor theatre is really not that important. It's the screen size, screen type, quality of lens and the rest of the hardware that is important.

I am sure some others will verify that, and others might not. But in any event, I probably would take their recommendations just to be on the safe side.
 

---

Posted by Daryl C. W. O'Shea (Member # 1303) on 02-24-2003, 11:47 PM:
 
You might want to look at these screen sizes.



Top only masking should work OK on a 60' screen. Some of our theatres have it on 58' screens. Of course I hate top masking, but it's a compromise.
 

---

Posted by Paul G. Thompson (Member # 655) on 02-25-2003, 12:24 AM:
 
Top masking only is still cheezy. It still involves farting around with the framing knob when you switch form flat to scope, or vice versa.

Some theatres use flat previews with a scope movie....see the problem?
 

---

Posted by Brad Miller (Member # 2) on 02-25-2003, 12:25 AM:
 
You're going to have to be more specific as to what kind of screen this will be used with, what kind of lenses you are using and most importantly, what kind of lamphouse you are going to run. Not all equipment is made alike, so 4000 watts of one equipment setup may be what it takes to equal 2000 watts of another.

Paul, if the lenses are set up properly, you will not have to touch the framing control on a top masking house when you change formats. The installation tech should line the turret up to compensate before cutting the plates or should shim the lenses in single-lens projectors before cutting the plates. Sadly I don't see this done too often. I hate lazy techs almost as much as I hate top masking auditoriums.

Manny, regardless top masking sucks, sucks, sucks. Don't do it! I would also recommend overspec'ing your lamphouses for the job. As time goes on, the actual reflected light will diminish due to the screen, lenses and reflector. It is much better to overdo the lamphouse such that you can run a brand new theater at 80% power with 16+ footlamberts of light on the screen. As the theater ages, you can turn things up to compensate without falling out of SMPTE spec. It is ALWAYS better to error on the "too much" side than it is to error on the "not enough" side.
 

---

Posted by Daryl C. W. O'Shea (Member # 1303) on 02-25-2003, 12:27 AM:
 
My Schneider and ISCO lenses don't require me to reframe for the top masking. Both aperatures have the same center line. You just have to adjust the lens to make it work.

Of course, I still hate top masking mostly because you end up with a flat picture that is way too high for comfortable viewing and you usually end up with an under-lit flat picture.
 

---

Posted by Paul G. Thompson (Member # 655) on 02-25-2003, 12:51 AM:
 
Good point, Brad. I was referring to the old manual swapping. Thanks for pointing that out. Mine won't shim worth a damn on my worn out Cineshitties or 1955 vintage XL's. Last time I tried to shim between the lens and the bushing, I couldn't even make the lens bushing fit in the projector without driving it in with a hammer.
 

---

Posted by Manny Knowles (Member # 1171) on 02-25-2003, 06:48 AM:
 
Wow! Thanks for all the input.

I went with 2:1 for the sake of simplifying the math at this stage. I'm not even 100% sure of those dimensions. They are close approximations based on the planned width of the room minus about 10 feet (and then rounded down to the nearest 10 feet).

By the way...Is it best to estimate lamphouse power based on the planned flat dimensions, or scope? I ask because they are not equally efficient formats. As I'm sure you know, flat gets a dimmer picture due to reduced light output.

The main thing was the 5W/sq. ft thing. I kind-of panicked when I saw 9kW! (I'm with Darryl: I doubt that will actually happen.) However, that 60-foot screen is not too far from what they've got planned, which is what started me looking into the wattage requirements.

Brad, I am with you on the overspec approach. I was going to ask later about a multiplication factor but you've already suggested, so that takes care of that! Thanks.

What do we do about this 60-foot-9kW-ain't-gonna-happen situation? My gut says "don't build it if you can't do it" but I'm just not sure they want to hear that. I remember reading somewhere on this site that larger screens "appear brighter" even when they're below 16fL. Did I remember correctly, and was that a factual claim?

As for masking: Some of these screens will probably have side masking and the little rooms will probably have no masking, which is common for these parts. (Flat images have blank space on either side of the screen. Not my idea, but it has become the norm here.) I worked at an AMC that had a "flipperboard" masking that swung up from the bottom for scope pictures and I didn't have to adjust the framing knob, but there were two things I didn't like about that. First, scope images were smaller than flat ones and then, as Paul pointed out, you have problems when you mix flat previews with a scope feature.

Lenses will be brand-new ISCO's -- mostly from their low-end, but the bigger houses will probably have the nicer lenses.
 

---

Posted by Steve Guttag (Member # 268) on 02-25-2003, 08:39 AM:
 
Manny,

A couple of flaws...ISCO has discontinued there lower line of lenses such that the Ultra-Star PLUS is what will be available (red lenses)

On the larger screens, consider a curved pearlescent screen. If curved properly you could get your 60-footer to meet SMPTE specs with reasonable sized lamps (5-6KW) depending on final screen dimensions.

Throw has absolutely no bearing on lamp size needed.

Steve
 

---

Posted by Dave Macaulay (Member # 813) on 02-25-2003, 09:09 AM:
 
Manny: I don't know your background so designing a cinema may be well within your abilities... if so, ignore this.
I just suggest you get an experienced designer to go over the plans and recommend the screen types and geometry, and give you lamphouse recommendations. Speaker and amplifier selection is another place where it's easy to either spend way too much on wasted capacity or get bad sound and plenty of blown equipment by trying to save too much money or using unsuitable stuff that sounds perfect in the marketing brochure.
The cost of a consultant is small compared to the cost of opening the cinema - or even fixing a serious design problem!
 

---

Posted by Manny Knowles (Member # 1171) on 02-25-2003, 09:37 AM:
 
Thanks for the additional input. I'd have to say this sure is one successful inquiry!

Steve: This is just a sketch, but it does indeed appear that someone is planning for curved screens. I will inquire as to whether that's just the way they indicate a screen or if they were specifically intending curved screens. I'd have to ask because I have seen curved screens on sketches that turned out to be flat screens in reality.

So...What's the word on "gain screens"? Love 'em or hate 'em?

Dave: Your point is well taken. I don't have the benefit of any formal training in theatre design theory. My background in design is limited to my real-world work experiences. This includes the various systems and design approaches that I have encountered and what I've liked/disliked about them. It also includes everything that I've learned here on Film-Tech in the last year or so.

I am sure that there will be others who are more experienced than myself giving their input, but it is part of my job to have some say-so in all of this. To that end, I am always interested in providing the best information available to me in the event that someone heeds whatever it is I have to say.

However, my experience (or lack thereof) notwithstanding, I often believe that I am alone when it comes to having the best interest of presentation at heart, as everyone else seems to be looking at the $$$ -- and this is evident, given all of the after-the-fact repairing, upgrading and "re-doing" that I've had to do over the years.

Still, that work has kept me gainfully employed so I suppose I shouldn't be so quick to complain.

As for sound systems, it's a safe bet I'll be asking for some input on that as soon as room dimensions are finalized. (Watch this space!)

With all due respect, what it all comes down to is that my experience has left me with a healthy skepticism when it comes to certain design experts (present company excluded, naturally).

Here's a thought: It's a longshot, but I will ask if they are interested in trying out a new consultant. If so, I will post a notice here on Film-Tech.
 

---

Posted by John Pytlak (Member # 331) on 02-25-2003, 10:00 AM:
 
The "5 watts per square foot" guideline is for a matte surface (gain=1) screen. If you use a gain screen, it should be properly curved and tilted using ray-tracing, or following the guidelines in SMPTE Recommended Practice RP95 "Installation of Gain Screens". A properly curved gain screen will allow the use of less power, since it is more efficient.
 

---

Posted by Manny Knowles (Member # 1171) on 02-25-2003, 10:07 AM:
 

quote:

---

If you use a gain screen, it should be properly curved and tilted using ray-tracing

---