[armystud0911]

I just watched a video, on the new Christie Duo projection system http://www.christiedigital.com/en-us/cinema/cinema-solutions-case-studies/christie-videos/Pages/Hoyts-Cinema.aspx they just installed two 30k+ lumen projectors in a cinema with a 90 foot wide screen, what I find interesting is that the rep from Christie mentioned that "at 100% power, we can get 6-8 fl across the whole image in 2D so- uh really bright image!".


We all know about the 16fl SMPTE spec, why is he calling an image that is roughly half that a "really bright image"?


Personally, I have found that I do not need a 16fl lambert image to seem bright, if I have a big screen, all I really need is 6-8fl and that does indeed seem "bright" to me in a light controlled room.

 

[Dankrakafoon]

Interesting.


After calibrating my Optoma HD20 (first experience with a projector), I ended up with 9.7 ftL at 100% on a 120" screen. I like the picture a lot and it seems plenty bright to me in a light controlled room.


However, note that I got this figure while measuring the greyscale off the screen with an e1 Display LT and ColorHCFR. Is this giving me somewhat accurate light output or do you absolutely need a dedicated light meter like DPs use?

 

[armystud0911]

There can be a lot of variance using a colorimeter, I wouldn't trust anything but a light meter, it very well could be 25fl.

 

[Dankrakafoon]

Ok thanks for the info.


BTW, in answer to your first question, I watched the video and I am pretty sure the rep said "we can get 16 foot-lamberts across the whole image in 2D..."

 

[armystud0911]

That would make a lot more sense, I still don't hear 16, but I could be not hearing him correctly. They must use some very high gain screens, at a native aspect ratio of 1.9:1, they need about 70,000 lumens to light up their screen with 16fl, seeing how their projectors emit exactly 34000 lumens each. I am sure they loose quite a bit after calibration as all of our projectors do, the gain would have to make up the difference.


It is very interesting because their site indicates that a single 34,000 lumen projector can light up a 105ft wide screen, why do they need 2 for a 90 foot wide screen then?


I see similar numbers from barco, they claim that a single 33,000 lumen projector can use a max screen of 105ft wide - and they even say that it tested 16 fl!


Now, even if these cinema projectors, that are ONLY used in cinemas can achieve every single lumen in the specs on screen, after calibration, they would need a screen gain of 2.8 to get 16fl. Seeing how most of these are AT applications, I have no idea how they can get anywhere near that much gain and even if they do, there would be absolutely insane hotspotting across the huge area the audience sits.

 

[AV_Integrated]

A 90 foot wide 1.9:1 screen is 90' x 47'4" which is 4,260 square feet.


4,260 x 16 = 68,160 lumens.


That's 34,000 lumens required per projector.


Now, the reality of 100% power and the rest, certainly could be 'made up', it may not be as better manufacturers tend to specify much closer to 'real world' lumen ratings instead of BS numbers. JVC, for example, in home theater tends to have lower numbers on their projectors, but do a better job with color when hitting those brightness claims.


When considering a $80,000+ projectors it is often important that the numbers claimed aren't such BS numbers as we are used to seeing as the engineering involved really needs to be accurate for the design. Still, with the Xenon lamps in use (typically) you get better color, more stable color, and more stable brightness that burns out more quickly, but provides a solid image throughout the life of the lamps. I would expect that these projectors really need minimal gain from the screen to deliver the image quality expected.


Still, theaters often run much dimmer than what we can achieve at home. They also don't have the contrast numbers we can get at home, or much else. It is a fact that home theater projectors in a good room can pretty easily best the local cinema in overall quality. From sound to image, we can do better.


Still, while I'm not sure they can't hit the numbers discussed, I'm as doubtful as you are that they actually are hitting anywhere near those numbers. Still, 12 lumens per square foot in a good theater environment is a lot better than 20 lumens per square foot in a weak room.

 

[PrimeTime]

Although "we can do better" at home versus theater, I'm inclined to believe that not many home theater setups have tamed their acoustical space (absorption, bass eigentones, surround deployment) sufficiently to match the audio of modern theaters.


(Then again, home theater denizens don't have to deal with cellphone-wielding patrons in the next row...)

 

[armystud0911]

Haha! That is one area that I find lacking most in commercial cinemas, love the big screen, don't care for the sound! Sure it sounds ok, but my home system has far more clarity and presence than the commercial cinema, plus, I have bass, they seem to forget subwoofers altogether. I did go to a THX certified theater once that had good sound, but none of the others match my current system. As far as the acoustic treatments go, they can be hit or miss, quite a few folks on here take great care with this, especially those with dedicated theaters, and commercial cinemas can do this well too, but a lot of it is helped by their larger room and not having to contend with speakers that are inches from viewers ears.

 

[PrimeTime]

My experience with commercial cinemas has been mostly IMAX venues, which have excellent audio. My only gripe is that some of them tend to crank the subs up too much, like it's a Car Audio competition. Probably the result of the comicbook/videogame genre we're now bombarded with at IMAX.


Most home video guys, even those who make an effort, run up against roomsize limitations such as bass modes/nodes that are baked into the smaller geometry of their space. Another compromise is the lack of a true center-channel speaker with non-AT screens.


Not to mention the video limitations of a light-colored room preferred by the spouse, and the (usually) attendant lack of absorptive surfaces that the wife often frowns upon.


And having some breathing room around the speakers, as noted, helps too -- especially with the surround radiators.

 

[AV_Integrated]

PrimeTime - I'm in agreement with both sides. The 'typical' movie theater doesn't best a well thought out home theater. Keep in mind that the 'rec room' theater that many people do rarely is as decent as a home theater, but even then, good components that are well cared for certainly can, and do, outperform movie theaters, and more importantly, you are always able to sit in the 'sweet spot' of the setup.


With that in mind, about the only movie theaters I'm willing to go to are IMAX because their sound is better and the projection setup is better. I am fortunate enough to have a true IMAX as my closest theater and a number of digital IMAX theaters within a short drive as well. But, for general movie watching if it isn't in IMAX I typically just wait for it to come to my home where I know I will enjoy the entire experience just a bit more.

 

[PrimeTime]

My main point is that components are overrated versus acoustics, which are consistently underestimated in their impact on audio quality.


It's been suggested that you're wasting your money with an expensive projector in a bright room. It's just as likely that you're wasting your money on expensive components (especially loudspeakers) in a smallish space with "live" acoustical properties, which describes many home setups.

 

[Bohanna]

A - Most home Theater audio set ups are far superior to typical movie theater set ups due to the simple fact that you have a lack of consistency and you are using audio equipment that is designed to project rather than reproduce sounds.

B- In A home theater you usually hear every channel in a more time aligned manner as opposed to a channel that could be on one side of the stage while you are on the opposite side. This is the reason Live Bands usually choose a mono house Mix. Musicians tried the live stereo route in the 70's and because of audience placement it was a colossal failure. - Bohanna

 

[PrimeTime]



Quote:
Originally Posted by Bohanna  /t/1519969/interesting-tidbit-about-brightness-in-theaters#post_24423371


A - Most home Theater audio set ups are far superior to typical movie theater set ups due to the simple fact that you have a lack of consistency and you are using audio equipment that is designed to project rather than reproduce sounds.

The main point (and fee structure) of "THX Certification" is to enforce standards in theaters. Professional audio gear of a given vintage is more consistent than consumer gear, and usually exhibits less measurable distortion than consumer gear.

Quote:
B- In A home theater you usually hear every channel in a more time aligned manner as opposed to a channel that could be on one side of the stage while you are on the opposite side. This is the reason Live Bands usually choose a mono house Mix. Musicians tried the live stereo route in the 70's and because of audience placement it was a colossal failure. - Bohanna

The early multichannel efforts of bands like Pink Floyd and the Grateful Dead were quite ahead of their time in that regard. Some venues may make multichannel house mixes problematic -- stage monitor spillover helps somewhat. Nevertheless, stereo house mixes remain popular.


And time alignment is a moot point when an actual center channel, placed behind an acoustically transparent screen in a cinema, can place the on-screen "image" exactly where it needs to be.

 

[Bohanna]

I wasn't talking about distortion I was talking about the Physics involved using pro audio gear that's primarily designed to project over longer distances. Time alignment is relevant if you have the same sound coming out of several locations at the same time. Maybe this will change when the acoustics of theatres begin to defy the laws of Physics. Until then the problem of the guy nearest the speakers hearing it too loud and the guy at the back of the room not hearing it loud enough will continue to be the primary concern of the theater owners and NOT audio fidelity like the home theater owner. Stereo house mixes are popular because they make stereo amps and there are full signal left and right output channels on most equipment. _ Bohanna

 

[PrimeTime]



Quote:
Originally Posted by Bohanna  /t/1519969/interesting-tidbit-about-brightness-in-theaters#post_24427308


Time alignment is relevant if you have the same sound coming out of several locations at the same time.

If you're referring to the physical alignment of multiple voice coils within a given loudspeaker unit, that's certainly true, and desirable.


However, identical sound radiating from multiple discrete sources (modules) is subject to the physics of interference (along the axis connecting the sources) and its accompanying peaks and nulls in frequency response. And is the primary reason why vertical arrays have become standard for sound reinforcement.

 

[Bohanna]

You will NOT notice any difference of multiple voice coils , You WILL notice the crossover slope and the comparable efficiency differences between various components. I was referring to the EXACT same sound coming out of loudspeakers placed in different locations. This is where you have the time alignment issues.- Bohanna

 

[PrimeTime]

Indeed, if there are two separate sources with the same input, and the listener is not precisely located equidistant from each source, you will have different arrival times for the radiating sounds and, hence, phase interference. Yeah, I guess you could call that a "time alignment" issue. So...


...strictly speaking, you are correct. It's just that the term "time alignment" is presumed to apply to phase-coherency among band-limited radiators within a given loudspeaker module. "Time alignment" as you use it will be an issue for anyone who is not precisely located in the "sweet spot" between the two sources. (And, BTW, is another reason for live sound reinforcement to evolve to discrete multichannel mixing a la Grateful Dead. But I digress...)


To return to the subject at hand (home theater versus commercial cinema), this is likely to be more of an issue in the home because of the close proximity of the radiators compared to the commercial cinema. Which is to say, if you move one seat over in a cinema house, the "time alignment" (as you use the term) will be degraded by a smaller amount than in a typical home theater room, simply due to the smaller geometry of that space.

 

[Bohanna]

Wow!! All these fancy terms just to get it wrong. Most home theaters are in small rooms that are surrounded with lots of baffling materials. The chance of a reflective surface in a home theater causing a reverberating sound to be be out of phase with the original is pretty much nil. The chances of a the SAME sound coming from multiple sources in a movie theater is far greater. The listener will hear both. The bigger the theater the more likely the problem. - Bohanna

 

[PrimeTime]

I wasn't talking about early reflections, which is apparently your focus.


I'm talking about the direct path distance differences in the two situations. If you do the math (I've written simple programs that calculate this), you will realize that the closer you get to the (two) radiators, the more phase shift (and, hence, interference) you will get for a given, incremental sideways spacing away from the equidistant position (sweet spot).


(Hope that wasn't too fancy...)

 

[armystud0911]