Film-Tech Forum ARCHIVE: IMAX DMR Aspect Ratio Question

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Posted by John French (Member # 8349) on 08-27-2014, 08:10 PM:

I saw a marathon of the Dark Knight films a couple months ago at the BFI IMAX in London, all on 15/70 IMAX film. I noticed something seemed a bit off with the 35mm-sourced scenes. The aspect ratio looked more like 1.85:1 than the 2.35:1 they should have been. At first I thought the enormous size of the screen was playing tricks on me, but as I watched I became convinced that the composition felt 'off', as if those scenes had indeed been cropped to a narrower aspect ratio.

Am I just crazy? Did I misjudge things due to the immense width of the screen? Or were the 35mm scenes cropped to fill a bit more of the tall IMAX screen?

Posted by Terry Lynn-Stevens (Member # 7349) on 08-27-2014, 10:20 PM:

Yup you are crazy! Lol

The 2:35.1 scenes should not look like 1.85 at all.

How did the prints look?

What did you think of the whole experience?

15/70 IMAX is a wonderful experience that really amazes everytime I see it.

Posted by John French (Member # 8349) on 08-28-2014, 04:30 AM:

The prints looked mostly great, although I noticed a fairly large amount of dust, and it seemed like it took longer to go away than usual. I believe in IMAX there's actually a person watching the screen the whole time and hitting a button to move a lens up and down to remove dust when it appears–I guess I can't blame them for having some trouble paying attention for a 8-hour marathon starting at midnight!

My biggest complaint was the timing–I wish it had run from 6PM to 2AM instead of midnight to 8. I'm a night owl but not that much of one…

I'd seen Rises in 15/70 before, when it released, at the Jordan's Furniture in Massachusetts (which has since gone over to digital, unfortunately). I'd only seen Dark Knight in DLP and 35, so seeing that in IMAX was a treat, especially given how nasty the Blu-Ray transfer is.

I love IMAX for the scenes shot on 15/70, but I feel like the composition of the 35mm scenes does not translate well to such a huge screen. I'd almost rather they windowboxed the 35mm scenes so they'd be more the size of a regular screen, letting you take in the whole frame. I guess I'll have to try for a seat further back if I can find somewhere to see Interstellar in 15/70 (although I'm guessing that'll mean a trip down to NYC…)

Posted by Terry Lynn-Stevens (Member # 7349) on 08-29-2014, 12:55 PM:

quote:
I love IMAX for the scenes shot on 15/70, but I feel like the composition of the 35mm scenes does not translate well to such a huge screen. I'd almost rather they windowboxed the 35mm scenes so they'd be more the size of a regular screen, letting you take in the whole frame. I guess I'll have to try for a seat further back if I can find somewhere to see Interstellar in 15/70 (although I'm guessing that'll mean a trip down to NYC…)

I am really glad you enjoyed the experience.

Posted by Marcel Birgelen (Member # 6801) on 08-29-2014, 02:41 PM:

I've also seen both the Dark Knight and the Dark Knight Rises at the BFI IMAX in London. Although they do have a digital install since a year or so, they remain one of the very few venues in Europe that still show full length 15/70 IMAX features.

quote: John French
Am I just crazy? Did I misjudge things due to the immense width of the screen? Or were the 35mm scenes cropped to fill a bit more of the tall IMAX screen?

Unless they messed up something rather terribly (and I doubt that), you did misjudge the aspect ratio of the 35mm scope scenes and the "hugeness" of the screen might indeed have contributed to it.

quote: John French
I love IMAX for the scenes shot on 15/70, but I feel like the composition of the 35mm scenes does not translate well to such a huge screen. I'd almost rather they windowboxed the 35mm scenes so they'd be more the size of a regular screen, letting you take in the whole frame.

I agree with you, I also don't like the constant aspect ratio flip-flop. The Dark Knight Rises has more scenes in native 15/70 IMAX and although that movie is probably the weakest of the two, it feels bolder and greater when viewed in IMAX.

The 35mm scenes feel cramped, narrow, like looking through a slit and every time it flips "back" to 15/70 it feels like the world is opening up.

I don't think it's a good idea to blow up those 35mm shots even more though. DMR or not, the picture already looks sufficiently blurry and grainy when blown out of proportions this way. Also, the 35mm composition would greatly suffer and most people will only get to see the scope version anyway.

In my opinion, a movie should pick one aspect ratio and stick to it.

Posted by John French (Member # 8349) on 08-29-2014, 03:00 PM:

I agree that the ideal would be to have the entire film in 15/70. From what I've heard Chris Nolan would have preferred to do it that way too, except that the IMAX cameras make too much noise for dialogue scenes (and I imagine the cost of all that film was probably a factor too!)

I am not as bothered by the changing aspect ratios as most people are (I've heard even more whining about the blu-ray release doing this than the IMAX release). What bothered me most of all was just that the composition of the 35mm scope scenes does not look right when the screen is so wide that the edges of the frame are in your peripheral vision. It wasn't that it felt too small: if anything it felt too BIG. The IMAX shots were composed for exactly that kind of presentation, and worked very well, and were immersive. But the 35mm scenes felt too big. I had to move my eyes around constantly just to understand what was going on in the frame.

I was fairly close to the front though (maybe 1/3 of the way up) because that was the only seat near the centerline left when I bought tickets (BFI IMAX uses reserved seating). While I like to be about there in most theatres, I have heard (and I believe it) that the best seats in a real, purpose-built IMAX theatre are towards the back. I'll have to try for that in the future.

Posted by Terry Lynn-Stevens (Member # 7349) on 08-29-2014, 04:17 PM:

John, what was your impression of the Dark Knight sound in the IMAX sound system? And do you like the sound lay out?

Posted by John French (Member # 8349) on 08-29-2014, 05:34 PM:

I thought the sound was great. I've seen some people arguing against IMAX sound in this forum, but I've always loved it. That said the criticism people usually seem to bring against it is that there's too much treble and it sounds too harsh. My tastes generally favor 'bright' sound so I guess IMAX fits my tastes pretty well.

As for the layout, I know IMAX uses a top-center speaker. I've never noticed this having any effect while actually watching a film, I've just heard about it and seen it when they light up the speakers before the show (and when I toured the IMAX dome in Boston).

I'm curious about IMAX's use of single speaker cabinets for each surround channel instead of the more typical wall arrays. It seems like that sort of a setup ought to produce more coherent sound from the surround channels, since the individual speakers are much larger and presumably higher-quality than each of the many smaller speakers in a typical surround setup, and there are not many speakers potentially interfering with each other. What are the tradeoffs of an IMAX-type single-speaker-per-channel surround system, vs. the more typical speaker array style?

My only complaint about the sound is I feel like it was a bit too loud, which is another common complaint against IMAX. Are IMAX theatres required to play at reference levels? Are those reference levels the same as the reference levels for DCP or for film?

Posted by Terry Lynn-Stevens (Member # 7349) on 08-29-2014, 09:38 PM:

quote: John French
As for the layout, I know IMAX uses a top-center speaker. I've never noticed this having any effect while actually watching a film, I've just heard about it and seen it when they light up the speakers before the show (and when I toured the IMAX dome in Boston).

I don't believe IMAX uses or used the top center speaker for 15/70 DMR films, I believe it was only used for 15/70 documentaries.

quote: John French
I'm curious about IMAX's use of single speaker cabinets for each surround channel instead of the more typical wall arrays. It seems like that sort of a setup ought to produce more coherent sound from the surround channels, since the individual speakers are much larger and presumably higher-quality than each of the many smaller speakers in a typical surround setup, and there are not many speakers potentially interfering with each other.

That would be the whole point of the IMAX surrounds, precise localization.

quote: John French
My only complaint about the sound is I feel like it was a bit too loud, which is another common complaint against IMAX. Are IMAX theatres required to play at reference levels?

I have never had any issues with IMAX sound for 15/70 purpose built locations, however I can see why digital IMAX turns off some people.

How big is the screen at the BFI?

Posted by John French (Member # 8349) on 08-29-2014, 09:46 PM:

The screen is 20m by 26m, so it's one of the larger screens even amongst purpose-built IMAX theatres. Maybe I found the sound a bit too loud because I was watching loud, action-packed films when my body wanted to be fast asleep in bed! I suppose it's also harder on the ears to listen to the soundtrack of a film full of explosions and gunshots at high levels for 8 hours than it is to listen to a narrator's voice and soothing music for the duration of a 40-minute documentary…

Posted by Terry Lynn-Stevens (Member # 7349) on 08-29-2014, 09:59 PM:

quote:
I suppose it's also harder on the ears to listen to the soundtrack of a film full of explosions and gunshots at high levels for 8 hours than it is to listen to a narrator's voice and soothing music for the duration of a 40-minute documentary…

I imagine that is the case. The documentary sound always sounded great to me.

Modern action movies are usually mixed way too loud to begin with. Throw into IMAX and it is even louder. That being said, some of the movies like Gravity sounded very good in IMAX, but then again I always say the mixing and recorded levels are what is important.

Posted by Brad Miller (Member # 2) on 08-30-2014, 04:40 AM:

IMAX systems don't make the movie louder. The poor quality of them makes them SEEM louder because they are so shrill sounding.

Also you must be deaf if you thought the IMAX presentation of Gravity was better than any Atmos install.

So seriously, stop with the IMAX nonsense. It's so obvious you're on their marketing payroll.

Posted by Marcel Birgelen (Member # 6801) on 08-30-2014, 07:06 AM:

The reason I like 15/70 IMAX is because of the enormous resolution, not really because of the native aspect ratio. The height of the picture only works for a few scenes, but I really like wider ratios much more.

quote:
I agree that the ideal would be to have the entire film in 15/70. From what I've heard Chris Nolan would have preferred to do it that way too, except that the IMAX cameras make too much noise for dialogue scenes (and I imagine the cost of all that film was probably a factor too!)

For some reason, Nolan fell in love with 15/70 IMAX. The reasons why that format never caught on for feature productions are quite obvious: unworkable cameras, horrendous costs, difficult cinematography and just a limited number of venues that can show it in all its supposed glory.

So, why not shoot it ALL on 65mm for example? That worked well in the past and should still work today... At least that would bring back some consistency between shots. It's not just the aspect ratio flip-flop, but also the obvious change in film structure between shots. A movie is more than the medium itself. Actually, I do think that the medium should not distract from the movie itself. With this constant switcheroo, you make the limitations of technology extremely evident. It's great as a tech-demo for what 15/70 can do, but not the best choice for a movie.

Besides that, I still believe in proper masking. A movie should be masked according to its aspect ratio whenever possible. I know that for huge screens like native 15/70 IMAX screens that's almost impossible to accomplish, so I don't mind it as much there, but if aspect-ratio-flip-flop becomes the norm, proper masking becomes impossible.

quote: John French
As for the layout, I know IMAX uses a top-center speaker. I've never noticed this having any effect while actually watching a film, I've just heard about it and seen it when they light up the speakers before the show (and when I toured the IMAX dome in Boston).

The "height" channel is commonly used for narrations in documentaries. I doubt there is a single DMR release that uses that channel, because it would cause trouble with the common IMAX digital layout. Also, it would require a specific mix, now they can just use the 5.1 mix and IMAXify it by messing around with it. They don't need to invent new channels.

Maybe, in the future, they could take an object based mix and map it to whatever future sound system they might come up with.

quote: John French
I'm curious about IMAX's use of single speaker cabinets for each surround channel instead of the more typical wall arrays. It seems like that sort of a setup ought to produce more coherent sound from the surround channels, since the individual speakers are much larger and presumably higher-quality than each of the many smaller speakers in a typical surround setup, and there are not many speakers potentially interfering with each other. What are the tradeoffs of an IMAX-type single-speaker-per-channel surround system, vs. the more typical speaker array style?

If the "speaker array" thing has been implemented correctly and not by just slamming a few speakers against the wall at every odd position, interference should not be a noticeable problem.

I'm not a fan of IMAX sound. Most of those documentaries have just mediocre mixes and sound has never been the main attraction there. At current volume levels, it's like actors are screaming at you all the time. I love sound with great dynamic ranges. If it needs to be loud, it should be loud, but only then. Unfortunately, IMAX seems to compress everything into the upper-3dB-just-before-ear-shattering range for their DMR stuff.

The current IMAX sound system has a huge gap between the screen and the left and right surround. Also, those speakers are usually in the top corners of the auditorium and in high auditoriums, that just sounds odd.

The whole setup feels and sounds much more like a rock concert, especially at the volumes they're playing it. If I go to IMAX, I go there for the picture, not for the sound.

Posted by John French (Member # 8349) on 08-30-2014, 11:17 AM:

quote: Marcel Birgelen
I still believe in proper masking. A movie should be masked according to its aspect ratio whenever possible. I know that for huge screens like native 15/70 IMAX screens that's almost impossible to accomplish, so I don't mind it as much there, but if aspect-ratio-flip-flop becomes the norm, proper masking becomes impossible.

I agree that masking should be used when possible and that a lack of masking is more annoying on smaller screens. The Grand Budapest Hotel is a good example of this: bits of it are at 2.35:1 or 1.85:1, but most of the film is at 1.375:1, and there's no way to avoid pillarboxing because those few scenes in wider aspect ratios use more of the screen. I found that extremely distracting. I've also been to a few multiplexes which show 2.35:1 films on a 1.85:1 screen without masking. I was very disappointed. How common is that?

quote: Marcel Birgelen
The "height" channel is commonly used for narrations in documentaries.

Aha! Thank you. I'd always wondered what the point of having that channel was, and that makes a lot of sense.

quote: Marcel Birgelen
Unfortunately, IMAX seems to compress everything into the upper-3dB-just-before-ear-shattering range for their DMR stuff.

If they are indeed applying dynamic range compression, that would explain why things sound a bit too loud, and why it causes listening fatigue so quickly. If that's what's happening that's a real shame. I love the dynamic range of (good) film soundtracks. IMAX's system should be capable of reproducing it fantastically, so if they're crippling it by releasing compressed mixes, that's a real shame.

Posted by Terry Lynn-Stevens (Member # 7349) on 08-30-2014, 11:29 AM:

quote: John French
I've also been to a few multiplexes which show 2.35:1 films on a 1.85:1 screen without masking.

2.35 on a 1.85 screen without masking has never really bothered me, neither has the IMAX setup. The presentations that really bother me the most are the 2.35.1 scope presentations shown on flat screens with the masking set to flat.

quote: John French
I was very disappointed. How common is that?

It is getting more and more common, if you want to watch a movie in Atmos in my area, you must watch it with this set up. Almost every theater near me has at least one of these type screens installed.

Cineplex has also started renovating and building their new theaters without masking in all auditoriums.

Posted by Dick Vaughan (Member # 540) on 09-02-2014, 06:29 AM:

quote: Marcel Birgelen
The "height" channel is commonly used for narrations in documentaries

Channel 6, screen top centre channel, is not the commonly used narration channel on documentaries. Channel 3, screen centre channel, is the one used for most narration.

Channel 6 comes in to it's own when films include space shuttle launches, waterfalls etc where height is required as well as width.

Posted by Frank Angel (Member # 248) on 09-02-2014, 08:05 AM:

DMR conversions are a way of bastardizing what was an exceptional film format in order to keep a company afloat that was doomed if it remained unable to present Hollywood fare. 35mm conversions are NOT IMAX film, they are VIDEO recorded ONTO IMAX film format. You are not watching what the 15/70 format was noted for, i.e., its exceptional resolution. If you think DMR titles which are nothing more than a blow-up from a much lower resolution 35mm film format onto 15/70 film (and only onto part of the 15/70 geography) was a great experience, you really should see real IMAX films. It is like night and day. Now that they have digital projectors, it's just silly to run DMR converted 35mm film -- just run the damn thing as a DLP and keep everything in the digital realm and stop dicking around trying to bamboozel the public with smoke and mirrors that they are watching IMAX of old. Although I am sure IMAX carefully marketed those screenings as the "IMAX Experience," to lure in the unsuspecting -- another indication that IMAX has lost its soul.

As for the aspect ratio of converted 35mm Hollywood titles, IMAX can do whatever they want with the aspect ratio in the conversion. They can lop off the sides so they get more image on the screen so it's less obvious that they are presenting a scope aspect ratio on a nearly square screen that was NEVER INTENDED for a scope format.

Nobody is in the booth raising and lowering the lens; where do they get this stuff from?

Point-source surrounds was a way of doing surrounds in early 6 channel setups; I read in an white paper by THX in the SMPTE journal, that the early THX specs addressed the point-source surround as a valid configuration; in fact, the tone of that article sounded like it was the prefered way of doing 6 channel surround. That was quickly abandoned in favor of multiple side speaker setups, maybe because it simply was easier to mount many small speaker boxes than to beheamoths in each corner of the smaller multiplex rooms. And given the move today to even more speaker locations with systems like Atmos, the IMAX setup will soon be out classed as a premiere sound configuration. Without major changes, the can't certainly won't be able to do Atmos.

Posted by John French (Member # 8349) on 09-02-2014, 01:17 PM:

quote: Frank Angel
35mm conversions are NOT IMAX film, they are VIDEO recorded ONTO IMAX film format. You are not watching what the 15/70 format was noted for, i.e., its exceptional resolution. If you think DMR titles which are nothing more than a blow-up from a much lower resolution 35mm film format onto 15/70 film (and only onto part of the 15/70 geography) was a great experience, you really should see real IMAX films.

I have seen real IMAX films (documentaries), as well as DMR films (entirely shot on 35mm or digital and printed on IMAX film). In this case I'm talking about The Dark Knight, which is a combination of the two: about 40 minutes of the film was shot with IMAX cameras and does demonstrate the capabilities of IMAX quite nicely (although my original question was specifically about the portions of the film not shot with IMAX cameras).

quote: Frank Angel
Nobody is in the booth raising and lowering the lens; where do they get this stuff from?

I heard this directly from the projectionist at the Museum of Science in Boston. He even showed me a little area set into the side of the theatre where an attendant would sit, watching the screen for any problems (since in a dome theater, the booth is below the audience and has no way to actually see the screen). He also showed me the piece of glass (not the actual projection lens, but a curved piece of glass which I believe was somewhere in the area of the film gate) which moves up and down to remove dust. I am not sure exactly how it works or what it is for, but it definitely exists. It may have been explained to me poorly.

Edit: From Wikipedia:

quote:
The "field flattener" flattens the image field. The [field flattener] lens is twice the height of the film and connects to a pneumatic piston so it can be moved up or down while the projector is running. This way, if a piece of dust comes off the film and sticks to the lens, the projectionist can switch to the clean side of the lens at the push of a button. The lens also has "wiper bars" made of a felt or brush-like material which can wipe dust off the lens as it moves up or down.

This is consistent with what I was told and shown by the projectionist.

Posted by Adam Martin (Member # 641) on 09-02-2014, 03:58 PM:

quote: Dick Vaughan
Channel 6 comes in to it's own when films include space shuttle launches, waterfalls etc where height is required as well as width.

... or when Mufasa has something to say from heaven! [Razz]

Posted by Marcel Birgelen (Member # 6801) on 09-03-2014, 06:41 PM:

quote: Dick Vaughan
Channel 6, screen top centre channel, is not the commonly used narration channel on documentaries. Channel 3, screen centre channel, is the one used for most narration.

Well, I guess it was still at the discretion of the sound mixer and maybe "commonly" is the wrong word here and "often" would be more fitting. I've seen quite a few of those documentaries and for example Born to Be Wild, uses this channel for most of the narration, at least in both the Dutch and German dubbed versions. The dialogue obviously primarily uses the center channel.

And sure, it's also used for effects. The usage in normal IMAX presentations isn't very clear though, but it's quite obvious in OMNIMAX/IMAX Dome, probably because this channel is practically over the head of the audience in this configuration.