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» Film-Tech Forum   » Operations   » Large Format Forum   » Can someone give me a primer on IMAX 15/70 vs. IMAX digital vs. digital cinema (Page 1)

 
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Author Topic: Can someone give me a primer on IMAX 15/70 vs. IMAX digital vs. digital cinema
Justin Hamaker
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 - posted 05-30-2009 06:36 AM      Profile for Justin Hamaker   Author's Homepage   Email Justin Hamaker   Send New Private Message       Edit/Delete Post 
I've never seen an IMAX film in an IMAX theatre, so I don't really know how the experience is different from a regular movie. And to be perfectly honest, I don't know enough about IMAX to know if my subject makes sense.

One of the bigger questions I'm wondering about is how IMAX digital presentation compares to a regular digital cinema presentation - 2K or 4K.

I'm also wondering what exactly it means when major Hollywood releases are also released in IMAX.

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Mark Lensenmayer
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 - posted 05-30-2009 08:40 AM      Profile for Mark Lensenmayer   Email Mark Lensenmayer   Send New Private Message       Edit/Delete Post 
Classic IMAX (screens of approximately 60 x 80 feet) is an incredible experience. The image fills the entire field of vision (the "in-the-movie" effect often associated with CINERAMA) and is absolutly rock-steady. The early films often started off with very small pictures in the middle of the screen to lull the audience into thinking it is nothing special, then blooming to full-size as the picture takes off.

Classic IMAX 3-D is still the best of all 3-D systems. This system uses 2-strips of film with a tremendously bright image. The sample trailer for "PAINT MISBEHAVIN'" hung paint blobs right in front of the audience's eyes.

OMNIMAX, or IMAX DOME, projects the image onto a tilted dome. It's a great system with the right films, but tends to seriously distort straight lines. I don't believe there are any in commercial theatres.

MPX was the first mini-Imax. They wanted a system that would fit a standard multiplex. The screens are normally in the 30' by 55' range, MUCH shorter than the original systems. They also eliminated the top-center speaker from the original setup. A special automated projector was invented for this system. Image is very bright and solid. 3-D is also very good. Biggest problem was the large amount of film needed. 3-D releases would often come on over 90 reels and require a long time to process.

Imax-Digital is the newest and most-controversial. It also uses the smaller screens. The system uses 2-2K projectors. The controversy has arisen when people walk into a theatre and expect classic Imax, and they see only the shorter screens. Do to a projection problem, I have seen Digital-Imax with both one and two projectors and I could not see an obvious difference. To my eyes, there isn't much reason to spend an extra $5 dollars per ticket to see Digital-Imax with other theaters showing images as big or bigger with Digital projection. Sound is very good, but nothing really special.

So, if you get a chance to visit a classic IMAX theatre, go. It doesn't matter what film you see (except HAUNTED CASTLE, that's really bad), but go see something in the greatest motion picture process ever invented.

BUT, if its in a multiplex showing 2-D, you can do better other places.

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Fred Tucker
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 - posted 05-30-2009 04:48 PM      Profile for Fred Tucker   Email Fred Tucker   Send New Private Message       Edit/Delete Post 
At my theatre we have 35mm film, a 2k DLP & IMAX Digital. I have seen movies in classic 15/70mm IMAX before but have never seen a MPX projector other than pictures and a scrap piece of film that was given to me. I think to answer your question best it should be divided into 3 parts 1.) picture quality, 2.) sound quality & 3.) value.

1.) The most noticeable difference between 2k & IMAX-D is the brightness, actual resolution is the same (if not less due to the larger screen).

2.) Sound quality in IMAX-D is improved over the 2k DLP, mainly because its an entirely new system. New speakers & amps flat out sound better than the 10 year old EAW drivers & Crown amps that were replaced. Also, sound panels were hung on the side walls (back & front wall already had panels) to help eliminate reverb & bleeding into the auditorium next door.

3.) I really believe you are getting what you pay for. So long as you sit in the front 2/3 of an auditorium you receive a full field of view from the 55' screen where before you had to sit in the front 1/2. The picture is rock steady and the bass will shake your teeth, what more can you ask for.

Major hollywood releases that are released in IMAX have an additional 30-seconds or so of footage that was shot with an IMAX camera. The sound is also supposed to be remixed for IMAX-D (no compression). Other than those two items (& I'm sure there are other minor differences) not much is going to be noticeable to the common movie goer.

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Julio Roberto
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 - posted 05-30-2009 05:17 PM      Profile for Julio Roberto     Send New Private Message       Edit/Delete Post 
If you have never been to a "real" (traditional) Imax, you should try and go before they are all gone. As you know, (real) Imax projects specially shot films with huge cameras that make each frame the size of aprox. 7 35mm frames using special film projectors capable of filling the screen with a bright picture of large size and great quality.

Although for the longest time Imax was synonymous of this huge screen with bright 70mm film 15-perforation-long frames at 24fps, eventually, Imax also equipped a few theaters with a lower cost, lesser system using smaller film projection and smaller film sizes (MPX).

And now, even more recently, Imax started to migrate to all-digital installations. For these it has chosen to use two standard Christie DLP DCI projectors with some propietary hardware to keep them adjusted, to fill screens of a size only slightly larger than average for multiplexes, instead of the huge screens it was known for before.

Now, when a movie is projected on an Imax digital theater, two things can happen:

If it's a regular film finished and distributed in 2K digital, then, projecting it on an Imax system has little difference between your normal digital DCI multiplex. Only differences would be:

-Usually, a slightly larger screen. Using two projectors help in keeping the image bright.

-A potentially slightly less visible screen door effect. Since both projectors can not be 100.00% perfectly aligned, the screen doors from each one will sort-of blurr on the screen as they mix with the image from each-other-projectors.

-If the film is in 3D, you may be treated to a slightly better quality (better brightness, less ghosting, more color resolution, better color depth, no "flickering") than most of the other systems using only a single projector, except Sony, which also excells in many of those parameters in 3D.

Otherwise, it's the exact same 2K-resolution show you get in other theaters, I think.

But sometimes, Hollywood kajoons with Imax and releases a movie as an "Imax" film as well. In this other case, Imax receives film elements (master) directly instead of a precompressed 2K DCI package.

Imax then puts these digital files through their own "image enhancement" processing (grain reduction, smart upsize, smart sharpening), which they call digital remastering DMR, and which ouput they use to print films for their few remaining large format film-based theaters and whatever format (I don't know what it is) they choose for their digital-DCI servers, pbbly a standard 4K DCI package.

I don't know if there is any special processing when playing back those "imax remastered" packages on those servers. My guess, is that they are just downsized again to 2K and sent to each projector, but perhaps Imax sends the pixels in a checkerboard configuration to each one of their two projectors, obtaining a result potentially slightly better than your regular 2K projection with a single DCI projector, perhaps abtaining results similar to a hypothetical 2.5K projector.

Here are some links to info about it all (note that it has a few journalistic errors and has a pro-Imax brownosing tone to it;)):
http://gizmodo.com/5250780/how-regular-movies-become-imax-films
http://gizmodo.com/5271638/a-rare-tour-of-imax-cameras
http://gizmodo.com/5250625/cineplexes-getting-imax-but-is-it-imax-or-conspiracy

This is interesting read before Imax decided to go with two 2K projectors instead of two 4K projectors, like it originally intended:

http://www.secinfo.com/dRX7g.v1Ne.c.htm

If we are to believe that document, and it matches my own calculations, so I do believe it, 35mm (projected 1.85 cropped release print) offers a resolution that is slightly better than 2K (by, say, 5%-10% only), while 4K is almost twice as good as film, so it's a noticeable improvement for people sitting in the first 1/2 of most auditoriums.

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Fred Tucker
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 - posted 05-30-2009 06:21 PM      Profile for Fred Tucker   Email Fred Tucker   Send New Private Message       Edit/Delete Post 
Most but not all of the IMAX-D content is 4k. Not that it makes any difference since the projectors are only capable of 2k and the extra data is "thrown out" to quote IMAX tech support.

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Louis Bornwasser
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 - posted 05-30-2009 07:56 PM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
I'm sorry guys, but even the original Imax experience is only a small effort compared to Cinerama. I had a private screening at a museum IMAX and they said "Wasn't that wonderful?" I replied, "When will the 2 other screens appear.?" High quality picture, seldom full height, and the sound (Sonics) was inferior to the system I have been installing in 35mm houses. Their bass was distorted and the speakers rattled and bottomed out when the missile launched. Louis

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Fred Tucker
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 - posted 05-30-2009 08:10 PM      Profile for Fred Tucker   Email Fred Tucker   Send New Private Message       Edit/Delete Post 
Very true about not filling the screen top to bottom. I've watched a couple of real IMAX films at the Houston Museum of Natural Science but that was far too long ago for me to comment on sound quality. I have an audio whiz kid working as a projectionist (parents moved and not much of a studio recording scene in Houston) and he is very impressed with IMAX-D's sound. He claims to here no distortion, no clipping and great bass reflex. I'm sure IMAX has gone through a number of manufacturers over the years & hopefully improved in sound quality along the way.

BTW & FWIW I really wish I was old enough to have seen Cinerama back in its heyday. Now that I am in his industry I have developed a great appeciation for what it is and where its been its a shame accountants seem to be calling all the shots though.

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Geoff Jones
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 - posted 05-30-2009 08:44 PM      Profile for Geoff Jones   Author's Homepage     Send New Private Message       Edit/Delete Post 
quote: Fred Tucker
Major hollywood releases that are released in IMAX have an additional 30-seconds or so of footage that was shot with an IMAX camera.
Is this true? I know that The Dark Knight had about 30 MINUTES of footage shot with an IMAX camera, and Transformers 2: A Movie I Will Not See has a few minutes, but afaik, NO other IMAX presentations of regular hollywood features (non-museum) had any special footage. They are basically just 70MM blow-ups that go through some sort of filtering to have the grain reduced.

I also think that one or two had "alterations" made. Wasn't one of the SW Prequels a little shorter in IMAX? And wasn't Apollo 13 cropped to 1.85 to make more use of IMAX screen height?

Also, many IMAX theatres sometimes show 35mm prints on their IMAX screens.

My personal experience has been that IMAX theaters tend to be a little better maintained, perhaps because they are something of a flagship auditorium, or perhaps because of IMAX's involvement.

When you go see a hollywood feature on an IMAX screen, you know you're guaranteed that it will be on a big screen (at least until LieMax). At a typical 'plex, the feature you're seeing might be on a big screen, or it might be on a tiny shoebox.

And, as mentioned, because of the larger gauge film, the image is rock-solid.

From my experience, Imax presentations don't subject you to lame commercials for a half hour before showtime. That's almost worth the extra admission price right there. They also usually do a cool little pre-show demo that shows off the sound system and screen size, that really highlights the equipment.

My biggest complaint about Imax auditoriums is that the steep slope of the auditorium tends to limit (imo) the number of seats with my ideal sightlines, compared to more traditional configurations.

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Fred Tucker
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 - posted 05-30-2009 09:03 PM      Profile for Fred Tucker   Email Fred Tucker   Send New Private Message       Edit/Delete Post 
I was told 30 seconds on average, but now that you mention it probably wasnt the most relaible source.

As far as the incline of the stadium seating, no changes were made so typical AMC big house seating incline that you find everywhere else less several rows of front seats that were removed to make room for the larger screen.

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Caleb Johnstone-Cowan
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 - posted 05-30-2009 09:22 PM      Profile for Caleb Johnstone-Cowan   Email Caleb Johnstone-Cowan   Send New Private Message       Edit/Delete Post 
You don't get the 'wow' effect on DMR films because your entire field of vision isn't filled like it is on 15/70 shot IMAX. The image is letterboxed on the full screen as the film has been shot in a different aspect ratio. It is still a lot better than watching a conventional 35mm film even on a big screen. My usual viewing pattern is to watch our rehearsal of the 35mm copy of a film, then get tickets for the IMAX DMR version as soon as I can get decent seats.

The Dark Knight is the only Hollywood film with extensive 15/70 shot footage and that is a truly amazing experience. If the studios had the balls to shoot all their tentpoles in the format everyone would win, but my guess is there are too many inconveniences and not enough talent out there to do it. The documentary 'Cinerama Adventure' suggests this is why only a couple of narrative features were made in the three-strip format.

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Julio Roberto
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 - posted 05-30-2009 09:23 PM      Profile for Julio Roberto     Send New Private Message       Edit/Delete Post 
Yeah, The Dark Knight has been the only "Hollywood film" which actually made full use of short sequences shot in true Imax. Otherwise, "hollywood films" shown in Imax are often identical except they may have had their aspect ratios altered (made more square) or some scenes may have been 3D enhanced (like the superman and harry potter films) or stuff like that.

But most of the time, it's just the same thing.

With Apollo 13, IIRC, they didn't crop the image to make it more square from the theatrical release aspect. They just blew up the negative which was Super-35mm but shot with the whole frame in mind. So, it was actually the opposite: it was kept "as it" and blew up for Imax and it was "heavily" cropped for theatrical release.

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Adam Martin
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 - posted 05-30-2009 11:35 PM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
quote: Julio Roberto
and smaller film sizes (MPX)
Wrong. All Imax film-based systems use a 15/70 film frame.

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Julio Roberto
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 - posted 05-31-2009 12:10 AM      Profile for Julio Roberto     Send New Private Message       Edit/Delete Post 
quote: Adam Martin
Wrong. All Imax film-based systems use a 15/70 film frame.
Well, not really. All the Imax ridefilm theatres used 35mm (3D) film running side-by-side (Vistavision style) 8/35.

Here is a list of Imax films, some of which were in that format:

http://us.imdb.de/keyword/imax/ride-film/

Here is one with some talk on the technical details:

http://reboot.wikia.com/wiki/ReBoot:_The_Ride
quote:
First, the ridefilm is formatted entirely differently from the TV series. A full 180-degree surround output onto 35mm Vistavision film and projected onto a curved 14-foot screen, which meant the animators could only experience their animation as it would appear by looking through a fisheye lens.

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Brad Miller
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quote: Mark Lensenmayer
Classic IMAX (screens of approximately 60 x 80 feet) is an incredible experience. The image fills the entire field of vision
Not quite. I am one of those people born with two eyes, and as such my field of vision is much closer to a scope ratio than the "way-more-tall-than-necessary" IMAX format. When I watch IMAX movies, my vision is never fully encompassed. I can always see the bottom masking (because they frame the center of action too low) and the sides. It is the ridiculous height of the real-IMAX system that is a waste.

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Julio Roberto
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 - posted 05-31-2009 12:22 AM      Profile for Julio Roberto     Send New Private Message       Edit/Delete Post 
Not only is the height "a waste", but also the incredible size of the film frame, with a resolution that, if fully resolved, would be much more than any human could see from any position in an Imax theatre.

I have always imagined the birth of Imax like this: they found a way to make nice projectors running the film side-by-side. They figured "Vistavision" was too wide and decided to go with 70mm film. But the bad news is that they needed at least 15perforations to make the format anywhere near "wide", and yet it's still too tall. So they went with it and a huge screen since such a large frame can be aumented a lot before the grain and lack of resolution starts to be noticeable ....

To me, 8/70 is "just as good or bad for the average human" as Imax. No need to waste all that film. I guess Vistavision or perhaps 70mm/5perf was always the answer for widescreen presentations in terms of quality/price ... but never took off...

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