Film-Tech Forum ARCHIVE: Big 35mm screens

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Posted by Tim Asten (Member # 4051) on 03-10-2008, 07:44 PM:

I have just read about a 100 ft screen for 35mm in a Hoyts cinema in Oz. They use a Kinoton "E" series projector with an 8k lamp. Is it really possible to get a decent 35mm picture on a screen that big? I know it depends partly on the quality of the prints and lamp house set up and so on, but there must be a limit to how much light you can punch through a 35 frame without heat damage etc? We have a 60ft screen in our largest room and our Kinoton FP40 with a 7k lamp and schneider lenses provides a picture which is at best on the dim side and quite soft. I have yet to see a 35mm screen larger than ours but these even bigger screens seem to be on the increase. Are customers being ripped off thinking they are going to get a fantastic movie experience or has technology moved on in the last 6 or 7 years? Tim.

Posted by Steve Guttag (Member # 268) on 03-10-2008, 09:46 PM:

Odds are, the 7K lamp is LIMITING your light output. There is a correlation between the size of the source of the light and the smallest aperture you can fit it through. For more on the subject, look up Etandue.

Kinoton has the best optics with the lowest heat, I have found.

Furthermore, one has to match the lamp with the optics of the system! Yes, the same lamp in a different lamphouse using possibly different lenses will yield different results. I've found some 5K lamps that work well with say a Strong 15" reflector but put out LESS light than a 4K lamp in say a Kinoton lamphouse!

In general, you will have more light throughput with a 6K lamp in a 35mm installation than a 7KW lamp. Not only will more light actually get through the aperture, less heat will be generated too.

There are some new lamps out and coming out that are based on super-short arc gaps...these lamps can be substantially brighter. For instance, I did some extensive testing on the ASL XM4202 lamp...you can expect it to bey close to 30% brighter than most ANY standard 4KHS type lamp in the same lamphouse (Kinoton). 30% is HUGE and the heat penalty for a 4200-watt over a 4KW is minimal and more than offset by the extra light.

I'm currently testing another high-brightness lamp (4500-watt) that is on the order of 40% brighter! In fact, this new 4500-watt lamp is putting out more light being run with only 3000-watts of power than a 5KW lamp running at just OVER 5KW (same manufacturer on the lamp). The temperture differnce at the aperture and in the lamphouse is substantial. Furthermore, it is only drawing 3/5ths the power...with electric prices nowadays, that can't be ignored.

So can you light up a 100-foot screen for 35mm? Depends on the screen (curved/flat and gain or not)...the lens and the optical system employed. I've tested lenses (same machine, same screen and refocused the lamp for best light on both using a PSA200 meter). I had one have the same light at f/2.1 as the other had at f/1.7. The f/2.1 lens had more resolution...when the f/1.7 lens was raised to f/2.1...the resolution evened out but the light was about 20% less. Note, this was only tested on one focal length...it may not hold true for other focal lengths.

I think, with a Kinoton Premier projector (notably better than a 50% shutter), ISCO Ultra Star PLUS lenses, 6K High Brightness lamp, and a screen with a gain at 1.8 or greater (and curved properly), yes, you could hit upwards of 13.5 to 16fL on a 41.8' x 100' screen. Now with that said...the throw would dictate what prime lens you would need and that may ruin it as you get to extreme focal lengths, compromises are often made to get the focal length.

Clearly this is a venue that screams for 70mm!

Steve

Posted by Rick Hunter (Member # 1606) on 03-11-2008, 03:36 AM:

I refer you to this topic...

Topic: Largest Permanent Screen Ever Installed in a Everyday Working Theatre

...in this forum.

Posted by Stu Jamieson (Member # 4626) on 03-11-2008, 04:07 AM:

quote: Tim Asten
I have just read about a 100 ft screen for 35mm in a Hoyts cinema in Oz. They use a Kinoton "E" series projector with an 8k lamp. Is it really possible to get a decent 35mm picture on a screen that big?

No.

Posted by Tim Asten (Member # 4051) on 03-11-2008, 11:30 AM:

It seems some of us have polarized opinions on giant screens. However, many thanks Steve for the useful information on the newer types of lamps and the fact that a bigger lamp does not automatically mean more light. I have heard of rooms with bigger screens than ours that use smaller lamps with apparent success. We may have to possibly adjust the lamphouse & ballast and experiment next time with say a 5 or 6k xenon and see what happens. [thumbsup]

Tim.

Posted by Phil Blake (Member # 2012) on 03-13-2008, 12:46 AM:

The screen at my first drive in was 148' x 42' high , we had a throw over 400' and the picture was really quite good.
It was lit initially with BTH carbon arcs which did struggle with light output and latter X60 strong xenons which produced excellent light on the large screen.

Posted by Jarrad Salmon (Member # 3818) on 03-17-2008, 06:10 AM:

I'm a bit late to this topic, but been absent for a while!

Hoyts at Blacktown is the cinema right? Haven't been there but have worked at the Greater Union Parramatta site with a 25 metre screen... They call it a G-Max cinema. The light output is the same as all of the smaller screens when tested/calibrated with the light meter. From memory it is only a 6K xennon, but don't quote me on that.

Picture was up to the standard of 35mm presentations.

EDIT: The projectors are the kinoton FP30 E's

Posted by Sean McKinnon (Member # 612) on 03-17-2008, 09:40 AM:

Steve,

I was told once that the reason you can't get as much light out of a 7+ K lamp is that the anode/cathode are too big causing you not to be able to focus the lamp down far enough to take advantage of the extra light? Is that BS or not?

Posted by Robert John Jeromson (Member # 2559) on 03-18-2008, 01:39 AM:

According to Guinness the largest "fixed" 35mm projection screen in the world resides at Hoyts Sylvia park in Auckland, New Zealand at 30.63m wide x 12.29m tall.

Posted by Alan Gouger (Member # 543) on 03-18-2008, 04:16 PM:

You guys are running some big a$$ screens in New Zealand:)

Posted by Louis Bornwasser (Member # 3063) on 03-19-2008, 11:16 AM:

Sean; in the 70's Strong sent out a paper showing "usable lumens." Super Lumex 2500 watt was the same as the X60 at 3000 watts. X60/4000 being slightly more. X60/7000 showed no more usable lumems than the 4k. 7000 had a lot more, but only with 70mm film.

The point was "no reason to go to 7 unless you are 70mm." Your resuls may vary depending upon bulb and reflector design. Louis

Posted by Jack Ondracek (Member # 1466) on 03-19-2008, 12:04 PM:

I don't have numbers for comparison, but I can say that we get much better performance from our Big Sky 7k lamps than I was getting from our X60/glass reflector @ 4k.

The picture is noticeably brighter, detail is better, AND the lamphouse allowed us to focus out the edges better. We're running these behind XLs and Schneiders.

From what I've heard around here, the Christie SLC should be able to produce the same results, though the only one I've seen in a drive-in is running old bulbs and is not maintained.

OK, maybe I'm not getting 16fL, but in a pitch dark drive-in, my 86 footer looks pretty darned nice.

Posted by Louis Bornwasser (Member # 3063) on 03-19-2008, 03:18 PM:

smpte std: drive in: 4-6 ft/lambert.

Your expensive reflector was designed with 35mm in mind. I do believe it is of European origin.

BTW: most large drive ins are X60/Century. Perhaps the X60 is not "best" except at 4kw. Louis

Posted by Jack Ondracek (Member # 1466) on 03-19-2008, 04:16 PM:

I've heard your observations about that reflector from several sources, Louis. It wouldn't surprise me. The light around the heat baffles does seem much more focused than with the X-60. I really did like the glass reflector on that lamp.

I've also heard the comment about the XL... maybe from you. I've got a Century head out here that I'll probably be trying, once I find the time.

Posted by David Kilderry (Member # 142) on 03-20-2008, 04:40 AM:

Jack our three drive-in screens are similar in size to yours, we run Strong X60 C, X 60 D and a Super 80 (essentially all the same size lamphouse, just from different years).

We run 5,000 watt lamps and get very good light for a drive-in, certainly better than the others in this state.

I have seen the 30 meter screen at Hoyts Blacktown multiplex in Sydney; it is very dull, even for screens this size. The lamp installed is either very old or poorly aligned.

The 30 meter screen just near here at Village Knox V-Max is better, but has slipped in brightness in recent years and is certainly duller than ours.

I would have a spotmeter shootout with any of the local 25 meter plus width indoor screens v's our drive-in screens any night of the week, they simply do not maintain them to ensure the light is at the optimum level.

The Strongs correctly aligned and maintained with a 5k lamp are an excellent lamphouse for drive-in use. Various technicians with national experience have said our drive-in screens are better lit than just about any they have seen.

Fresh lamps are the key along with clean polished reflectors and someone who knows how to align a xenon lamphouse. The SMPTE spec (is it 192 M? - I forget) relating to drive-in light requirements being 4fl from any ramp position, would show up some indoor screens these days I think!

David

Posted by Jack Ondracek (Member # 1466) on 03-20-2008, 12:21 PM:

Hi, David.
I would agree with your observations of the X-60 series lamphouses. Mine had aged to the point that they needed to be torn down and rebuilt. If I had the time and inclination to do that, I probably would still be happily running them. Instead, I went another direction and replaced them over time. Of the three I had, the one with the glass reflector was by far the best. On the other hand, my understanding is you can't get those anymore, and that would have been a real problem for me, if a bulb had blown.

Posted by Jeffry L. Johnson (Member # 453) on 03-22-2008, 01:33 PM:

quote: Louis Bornwasser
smpte std: drive in: 4-6 ft/lambert.

No, the SMPTE standard is 16 footlamberts. RP 12, Screen Luminance for Drive-In Theaters, clause 4.2 allows a minimum luminance at the center of the screen of 7 fL as measured from the central position. Clause 4.3 states:

quote:
When maximum compromise must be made... the luminance at the center of the screen, measured from any car position, shall in no case be less than 4.5 fL (15 cd/m^2).

Posted by Ron Funderburg (Member # 4561) on 03-22-2008, 01:53 PM:

When I owned theaters I converted my 8 screen theater to use Technolight at 2000 watt. We had 38 feet wide screens and only about 50 foot throws and the 2000's in the lamp houses we had just were not getting enough light on the screens. They changed out the guts of the light house and put in their technolight glass reflectors and the light amount on the screen was wonderful. We were told that the 2000 watt bulb would now put out as much a 3000 watt for that distance and size of screen. I was happy with the picture on the screen but I never did find out if the claim from technolight was true.