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Author Topic: Screen: Common Height or Common Width? Amanda Mundin Expert Film Handler Posts: 122 From: Belper, Derbyshire, UK Registered: Sep 2005 posted 05-31-2014 12:30 PM                     Are people able to get 14fl in both 2.39 and 1.85 by just adjusting lamp current or do they usually sacrifice one of the formats, either under-lighting 2.39 or over-lighting 1.85? (Assuming common height screen) Steve seems to suggest on the first page that if you're getting 14fl in 2.39, 1.85 will be in the region of 22fl. Looking at the Operating Range Christie suggest that most of their bulbs will only operate between 70% - 100% which doesn't seem enough to match the two formats on paper.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-31-2014 08:22 PM                     Amanda, your analysis is right on the money. For common height screens, it is impossible to hit 14fL on both because there isn't enough range in the lamp...particularly throughout the lamp's life. Furthermore, swinging the lamp current like that is not doing your lamp any favors and will certainly shorten lamp life and lead to hard striking and flame-out.  |  IP: Logged Mattias Mattsson Film Handler Posts: 90 From: Göteborg, Sweden Registered: May 2007 posted 05-31-2014 10:15 PM                     Philips has some new bulbs ("Helios") that is supposed to have a wider operating current span, at least the Barco variant. The XDC-4200-BH is specified as 80-160 Ampere: http://download.p4c.philips.com/l4b/9/928416906301_eu/928416906301_eu_pss_aenaa.pdf Does anyone have experience with these?  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 06-01-2014 12:21 AM                     I ran a variant of the 4200w Philips bulbs in an NEC 2500 and they held up very well. Outside of light getting rather flat looking when time for warranty change, the envelope stayed clear. Yet, the Philips XDC-4200S for the SONY's were terrible. They'd lose half their light before they'd hit half of their warranty hours, being of 700 hours. When you pull the bulb, the envelope was almost black as pitch-mainly due to the poor cooling these SONYS were known for.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-01-2014 07:33 AM                     quote: Amanda Mundin Are people able to get 14fl in both 2.39 and 1.85 by just adjusting lamp current or do they usually sacrifice one of the formats, either under-lighting 2.39 or over-lighting 1.85? (Assuming common height screen) DCI/SMPTE spec for cinema is not 14fl center, but 14fL +/- 3fL. And some more variance is allowed off center (which no one installing silver screens cares about anyway). So, which part of the spec do we consider 'hard' or 'soft' to follow? You shouldn't care that much about a little bit of over or under lighting. No one pays you for being right on 14fL. Operational needs in this case should be considered first. As is the case in the majority of installations. - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-01-2014 05:57 PM                     Well NO! You ARE being paid to show the image at 14fL...that IS the spec. Review rooms, in fact have a much tighter tolerance of .7fL because any deviation from the spec will affect the overall presentation. When someone buys a ticket, they should expect that the theatre is showing the image in an optimal fashion. So is your position that one should show Scope at 11fL and Flat at 17fL because that is the swing in the tolerance? Is it your belief that was the intent? Do you not see the issue of always presenting the scope image in an under-lit situation? Add into that gain screens that manufacturers are now pushing so you get the sides/corners down to 70% of center so the scope image gets down to 7.7fL at the extremities. I guess it is always an overcast day in that theatre. But even with that sort of "method" good luck holding it at a mere 6fL spread. If the target was a mere 11fL for Scope...I wonder how well it will stay there...even with the various forms of "CLO." Just because a specification has a tolerance, does not mean that an extreme part of the tolerance is where one should target. I personally, think +/- 3fL is too wide and should be tightened to 2fL because with digital...if one slips in either direction one has issues with either the whites or the blacks depending on which way one shifts.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 06-01-2014 06:11 PM                     It's gone a bit crazy with digital. Film projection: the color temperature was ... whatever it was. Strong started supplying super bright reflectors that are also very blue. Nobody yelled about it, they had bright (and blue) images. Brightness... pretty much whatever you had, ft-L meters were very rare except for Imax techs. So now we have to calibrate colors and set screen brightness for the video projectors... color because it's adjustable and brightness because... well, who knows? because the color meter reads brightness as well? I suppose peoples eyes have suddenly become more discerning? Not likely. And - if the spec is 14 ft-L +/-3 then YES 11 scope and 17 flat is just fine. There are a lot of 3D screens where the 2D picture is 20-40 ft-L at minimum lamp power, assuming they don't show 2D through the 3D system (hah!). Nobody complains. The DCI police have yet to drop by. Specs are a great thing. When few screens meet the specs but nobody cares, maybe the specs should be revised.  |  IP: Logged Antti Nayha Master Film Handler Posts: 268 From: Helsinki, Finland Registered: Oct 2008 posted 06-02-2014 01:30 AM                     If you can run your lamp at 70% for flat and 100% for scope, you will almost even out the light levels. I usually find that there remains a light difference of about 1 fL, which I've decided is good enough. That said, going between 11 and 17 fL would be a bit much for me. And anything higher than that looks terrible – I do and have complained about gross over-brightness.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-02-2014 05:07 AM                     quote: Steve Guttag Well NO! You ARE being paid to show the image at 14fL...that IS the spec. No, she's being paid to show the image between 11fL and 17fL center peak lumen - THAT is the spec, you know it, you read it. That's why it says +/- 3fL theatrical. You're not okay with 11fL? Even less off-center (70%)? Why? It's in the spec! Do you follow your own spec? Steve - how many of your installs keep 14fL for every picture format over the full lifetime of the lamp? The only way to do it is using anamorphics or constant wide screens. Do you endorse these two methods as the ultimate way to do digital cinema? Do you decide not to do the job, not to project the DCP, send people home, if these two methods are not possible/allowed/wanted? The spec doesn't reference ambient lighting, effective projector contrast, black level, etc. I do not endorse underlighting of screens. Certainly not as a measure to NOT overlight a screen. But the spec in itself allows for 6fL of variance already. So what are we talking about? Do we declare common height screens as non-DCI compliant? - Carsten  |  IP: Logged Amanda Mundin Expert Film Handler Posts: 122 From: Belper, Derbyshire, UK Registered: Sep 2005 posted 06-02-2014 05:37 AM                     Why don't the lens manufacturers install an iris inside the lenses as in camera lenses? Surely the iris could be automated, and moving a quarter stop or third of a stop at a time would go a long way to balancing light output, then varying lamp current could be used for a final tweak to hit spec.  Wouldn't have thought cost would be prohibitive as they already install them in much cheaper SLR lenses etc.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-02-2014 06:47 AM                     The realities are that once you go above 1.3 in the gain of the screen, you are out of DCI spec on the sides/corners. So lets not kid ourselves...11fL in the center...if that is the target means that it will not be there after the installer is done and the lamp decays...the tolerance is to allow for such realities. Nowhere will you read in the spec to target for the bottom end of the spec (or the top). They don't specify that "Flat" is 17fL and Scope is 11fL...14fL is the spec for all shows. Every screening I've done they have insisted on 14fL for EVERY FORMAT. 14fL is the spec...that is where you are supposed to be setting the light for every format. I think Amanda's idea of an iris in the lens is outstanding though it would require all lens manufactures and projector manufactures to get on board with it to control it. It would improve focus on the irised format. Personally, I agree that the industry is a bit overboard with the importance of the color balance, by and large. I can say from a studio point of view...it is something they definitely wanted in the film days...theatres always project too blue (Christie was the worst offender of the American companies). When the colors aren't right, the flesh tones aren't right and that is easy to pick off. I've found that the human brain is pretty good at adapting to that and just making it look normal...until the next reel change mucks it up again. With digital, we don't have that issue. I think that because we CAN set color and finally get that nagging thing right...it was codified and made of importance not because we can but because the studios always wanted it. Light levels have always been measured. Long before digital...maybe not in your theatre but in my 34 years, they have ALWAYS been measured. With film, 16fL has been the goal (+/- 3). If one went higher, you got pronounced flicker on a typical 2-wing shutter. If you go low, you lose detail and get the overcast day effect. With digital, we have an even tighter system in that if you go bright, you don't have the black level to hide it...if you go dark you still get an overcast and loose yet more black levels because the system couldn't reproduce it. I'll admit, with digital, (in the typical theatre, not screening rooms) I go on the bright side. Scope at 16 and flat as close as I can get because nobody complains about a bright picture and as the lamp ages...everything is going to shift down, not up. As for 3D...oh yeah people complain about the levels and when a 3D theatre with a high gain screen runs 2D...okay so they are at 20-30fL in the center...but in the corners they are down to 8...so it isn't right anywhere. It is a problem that degrades the movie going experience. I'm happy that some of our Dolby 3D (actually most) have 2D and 3D lamps/lamphouses so that the light levels are always optimized. They also don't waste their expensive 3D lamps running 2D. Naturally, this only helps if there are NO shows in 3D for that day...they don't switch on a show-by-show...but day-by-day...again, except screening rooms where each show is optimized. I honestly didn't know that you guys were using the spec in the manner you do...to let scope run at 11 and flat at 17. That may explain why I see so many under-speced systems that have no chance of showing at 14fL on scope. I guess it is a method.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-02-2014 11:07 AM                     Steve - make it short: When was your last common height installation with a zoom lens? How did you balance flat and scope brightness? What were your brightness readings after you finished? - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-02-2014 12:57 PM                     For a conventional theatre...14 scope, 21 flat. With anamorphic lens, 14 and 14. The spec is 14, not 11. If it was 11, the spec would read 11 +6/-0. Do you actually think that any movie is tested at 11fL to see if will look okay at that level? If so, you are delusional. I dislike not using an anamorphic in a common height theatre for just this reason and I've stated so many times. But if I'm going to err outside of spec...it will be in the too-bright, not too dark. Trust me, this discussion is going to come up the next time I'm at the proper committee meeting. It has been very enlightening as to what is really happening.  |  IP: Logged Amanda Mundin Expert Film Handler Posts: 122 From: Belper, Derbyshire, UK Registered: Sep 2005 posted 06-02-2014 01:56 PM                     Out of interest is anyone aware of any cinema in the UK that uses an anamorphic lens on a digital system to project Scope? It would be nice to see it in action  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-02-2014 02:40 PM                     Nothing 'is happening', Steve, you're making something up. No one confirmed putting scope at 11, no one endorses that. But the spec has a range, and no one ever believes that the idea behind the spec is that all formats have to come down at 14fL all the time. Features are mastered AT 14fL with the assumption that theaters MIGHT be as low as 11 or as high as 17. That's what's behind the +/- 3fL spec. DCI neither mandates the use of anamorphics nor constant width screens. So integrators have to work with a small, very limited equipment market that has been established so small because of the same spec. Over- or underlighting should be judged based on the projector/lens in use, perceivable contrast/ambient lighting, screen quality, etc. The more ambient light, the more overlighting is acceptable, the less ambient light, the more you can steer towards the lower side. Taking bulb-aging into account, there is no way to ever hit the spec the way you seem to suggest it. DCI could have easily mandated the use of anamorphic lenses for common height screens if they'd wanted it. There is a reason why they didn't. - Carsten  |  IP: Logged

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