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This topic comprises 2 pages: 1 2
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Topic: Image quality at a Cinema & home
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Ken Lackner
Phenomenal Film Handler
Posts: 1907
From: Atlanta, GA, USA
Registered: Sep 2001
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posted 07-13-2015 12:16 PM
quote: Bobby Henderson
In the case of premium big screen concepts like IMAX digital, they actually do things to deliberately de-focus the image to hide what would otherwise be a very obvious pixel grid blown up on a bigger than usual screen.
Bobby, where did you get that information from? I service and have patronized theaters with IMAX and other PLF auditoriums and have never heard of this happening or experienced it.
quote: Jim Cassedy
The lens focus servo systems on the digital projectors are pretty good, but, lets
face it, the DO drift a bit over a period of time.
quote: Marco Giustini
On top of that you have to add badly installed systems where lamps are not aligned, colours are not shot, brightness is not maintained and the list goes on and on.
These are more likely explanations. And if it's a 3D-equipped auditorium, it's entirely possible the 3D mechanism was left in place for a 2D presentation, which will have a detrimental affect on image quality.
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 07-13-2015 07:04 PM
quote: Calude S. Ayakawa
Gee, I did not know the thread I started would become so technical.
Well, this forum is basically a bunch of movie technicians, so the discussion turning technical is somewhat of an occupational hazard around here!
What we're doing is discussing precisely what you asked us to: the reasons why theatrical digital projection can sometimes look and/or sound subjectively "worse" then the same movie played on consumer media and equipment in the home. The bottom line is that there are a large number of variables and factors in play, and that one or a combination of them could be behind the disappointing show you experienced.
quote: Claude S. Ayakawa
Is there a possibility when cinema digital projectors gets used more and in service for many years the picture quality deminishes over time?
The intensity and quality of the light from a digital projector's xenon bulb drops off significantly over the course of its life, and it will also start to develop a flicker towards the end. In our largest theater, for example, we use 6kW bulbs. They are warrantied to 800 hours. For the first 300-350 they are very bright and steady. From 300-600ish, their light output diminishes. From around 600 they can start to develop a flicker. To maintain the best possible light, we would need to replace them after 300, but given that they cost over $1k each, we can't afford to do that (we usually do after 500-600).
If you time your visit for when we've just put a new bulb in, the picture will be super bright. But if you come to see a movie the night before we retire it, the picture will still be OK, not as good. There are, however, theaters out there that for whatever reason will run their bulbs past the "still OK" phase of their lives.
You may have had the bad luck to see a show lit by a totally worn-out projector bulb. If the image was dim and/or flickery, that's very likely. The projector may just have been underlit: the more powerful the bulb, the greater the cost per hour of illumination time, and so some theaters do underlight their screens. So the bulb may have been OK in terms of the hours it's done, but just not have been a big enough one to light the screen properly in the first place.
I don't know if the performance of the lenses diminishes over time (e.g. if coatings are degraded by prolonged heat exposure). Reflectors can become heat damaged. I can't think of any other reasons why a typical d-cinema projector shouldn't be delivering the same resolution and color depth from the same DCP after many years in service.
You may have seen a poorly mastered DCP (like the one of 2001 that we've been complaining about on F-T pretty much since it came out), with a low bitrate. Or, as Bobby suggests, it might have been that the operators at that theater believed that focus on a digital projector is just a case of "set and forget", and therefore it drifted over time.
quote: Claude S. Ayakawa
If what I now feel is true, it was very tragic when the motion picture industry abandoned film for crappy digital ptojection.
I'm sure you've seen some scratched up film prints played on poorly operated and maintained equipment in your time, right? Both systems are complex technologies, that are designed to need ongoing maintenance and upkeep investment to continue opearating at peak performance. If you care about image and sound quality, then as a customer, your best bet is to find the theaters that care about that, too. Admittedly that could be a challenge in a relatively isolated community such as Hawaii, but if there is enough demand, someone will come along to supply it.
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