Private film premiere in an IMAX

[simonza]

Hello everybody,

first of all: THANK YOU to the person or the group of people who is responsible for this awesome software! I really appreciate
it

I know there are some IMAX related posts here but mostly the author is asking for a very specific thing. My question is a little bit more general.

I live in the southwest of Germany and we a literally in IMAX heaven here. We have a 6394 ft2 and a 3767 ft2 screen less then 45min away from our home town.
And currently the biggest IMAX in the world gets build 30min from our home with a 11195 ft2 screen (no dome).
All three are (or will be) dual laser IMAX.

We are currently in pre production for a 40-50min indie-film and somebody had the crazy idea to hold the premiere at one of our great IMAX cinemas with all the cast and crew and their family and friends.

We are shooting on the Panasonic S1H "open gate" so in a 6K 3:2 format.

Our question would be now, if it is even possible to fill the whole 1,43:1 screen with a DCP of that size. Because I read somewhere here that for 1,43:1 screenings an anamorphic lens would be used. What would be the squeezing factor and would it even be possible for them to play a that from a "normal" DCP?

Of course we would be happy with 16:9 as some ads in that format even look better than the trailers that are playing before an IMAX movie. But 1,43:1 would a a very big "nice to have"
For 16:9 a "normal" 16:9 DCP would be enough, right?

Concerning the sound, we will not go beyond 5.1. It's not that action packed that we would consider 12.1 (and for budget reasons of course).


Thank you already for your answers and stay safe during that crazy times

Simon

[Carsten]

IMAX is quite special in that the sites have to follow IMAX corp constraints. Certain features of IMAX installations can only be used by DCPs that went through IMAX own mastering facility, e.g. 3D, and probably also full screen/1.43:1.

In general, you can only assume that a plain vanilla DCP can be played successfully there. That is to allow digital IMAX theatres to play general DCP trailers and mainstream content. I don't think you will be able to play anything there beyond a standard flat or scope 5.1 composition. 4k should be possible.

I guess you should try to generate a flat cropped test version of your content, and ask them for a try.

Actually little knowledge exists on the internet about how a digital IMAX operates technically. I have never seen a digital IMAX operator turn up on a forum and talk about things. One reason is, there are not many of them, another might be that they are not allowed to talk in public. A third reason is, IMAX is not telling their operators too many details, only as much as needed to run the systems.

This guy, memberlist.php?mode=viewprofile&u=626 obviously has access to an IMAX/Xenon installation.

- Carsten

[simonza]

Thank you Carsten for your answer (I can‘t respond to your message because I‘m a „new“ member here.

I was in good contact with one of the projectionists via email and in person when I saw TENET the 6 times haha

But we didn‘t talk about our film and now there is a lockdown.
He often talked about retirement so maybe our timing is bad here haha But one thing he often said is that they almost can‘t touch anything that comes from IMAX. They get the key for the drive at the morning of the premiere and they can just change the overall loudness. They can‘t touch the single channels.

Back to our film: You said that flat or scope should be fine.
We are trying to get as much as possible on the screen and that would be 16:9 right? All the adds before the movie are in that format. 16:9 is 1,78:1 and flat is 1:85, right?

So is a 16:9 DCP not a „plain vanilla“ DCP?

Sorry for the stupid questions but I‘m just starting out with DCPs

Thank you!

[Carsten]

Technically, 16:9 is not more than flat, but less - given standard digital cinema procedures.

Most cinemas play 16:9 content within their flat preset. A flat preset displays 1998*1080 pixels. 16:9 would fit into a flat container with lean pillar-box bars on left and right - 1920*1080. So, a 16:9 image would play same height, but slightly smaller width than flat.
(double all numbers for 4k)
Some few cinemas use dedicated 16:9 presets, projecting a 16:9 image slightly larger.
I doubt that an IMAX has special 16:9 presets, but it may possible. The trouble is, all common cinemas use common DCI server GUIs for presentation control, and it is quite easy to analyze what is going on during a show. IMAX uses the same servers (with some modifications), but hide the native GUI from their operators. Instead, they show a much simpler show control GUI to their operators which doesn't tell you much. There is a lot of secret sauce going on.

One would need to take a few test DCPs to an IMAX site in order to check what is actually going on with different formats. I wish I had an IMAX laser operator to talk to...

You may create a standard UHD aspect ratio DCP within a 4k flat container. 3840*2160 in a 3996*2160 container

It is possible to create 'native' 16:9 containers (1920*1080/3840*2160) after adjusting a setting in DCP-o-matic advanced prefs tab - but I would avoid them, they are non-standard, and could cause issues.

BTW - as far as I know, the S1H will only do 4:2:0 color at 6k/open gate. It may be worth using that mode if you absolutely need the extra reframing capability in post - otherwise, I would probably prefer C4K/DCI at 4:2:2. That will allow you to put your capture pixel raster 1:1 into the DCP.
If you shoot 6k/5952 x 3968, you need to crop and scale. The maximum resolution you can put into a DCP is 4096*2160. Crop&Scale is not so bad, but at some point, you need to make decisions towards how you frame your master anyway.


- Carsten

[simonza]

Ahhh great!! Thanks!

That would explain that all the 16:9 adds that still seem massive on a big IMAX screen, don‘t actually fill the whole screen horizontally. There is always a small gap.

I was always wondering about that.

Try to contact the IMAX in Sinsheim. They were very supportive with technical stuff in the past. I asked them A LOT on why they didn‘t keep the 15/70 film projectors haha

[Carsten]

Yes. Most real film-trailers use the standard flat or scope image widths. They are usually shot with cine cams that offer a real 2k capture. Some semipro cams like the GH5, S1H, etc. now also offer DCI/4K shooting modes. These special picture rasters do not add that much to actual resolution or perceived sharpness, but allow to fill the proper DCI containers and thus screen shapes.

Common ads are shot on FullHD/UHD cameras and only use the 1920*1080 or 3840*2160 raster. It is quite common for them to show these slim bars on the sides in cinemas. You can easily crop/scale them to cinema aspect ratios if you really want to fill the screen perfectly, but, it may go with some image loss and/or scaling artifacts.

[simonza]

If we don't shoot open gate with the S1H we will most certainly shoot with the NINJA V to get ProResRAW capabilities in 5.9K (max. 16:9).
Downscaling isn't a problem and is even more detailed than shooting direct in C4K.
We're just deciding what would be more beneficial: More color information/better codec or more wiggle room to change composition in post.

Correct me if I'm wrong but I think the C4K mode is in S35 not in full frame, right? I never use that mode so I don't know

And one final question about our film: I could avoid the small black bars on the left and on the right, if my non-DCP master is already in 1,85:1 right?
And that would be 3996x2160 right?

[Carsten]

Internally, the S1H can record C4K both full frame (scaled down from 6k) or cropped.

If you go with an external RAW recorder, it's your choice.

https://www.cined.com/content/uploads/2 ... S1H_01.jpg

As there is plenty of resolution, in my opinion it would be best to create a flat master for cinema/DCP.

- Carsten

[dargon_master]

Hey! Hopefully I'm not too late to help, I work as a projectionist and some content creation at a Dual Laser GT site.

IMAX is really no different than any other DCI system, they're just some technical tricks employed to achieve non-DCI standards. When you run a DCP not authored by IMAX it can run 4k, but only out of a single projector with 7.1 audio (although 12 channel is possible). If the content is longer than 30 minutes there will be a title card saying "This Is Not The IMAX Experience".

The way IMAX DCPs work is in their certs. The certs tell it to run dual projector, and can tell them to run at the 1.43 "laser squeeze" aspect ratio with the specific AR143 cert. To achieve this the source is originally rendered at 4096x2864, then squashed into a Full 4096x2160 container. So the image is vertically squeezed down about 25%, and the AR143 cert tells the Image Enhancer to do a digital anamorphic stretch to the 1.43 aspect ratio. The concept is similar to monitoring anamorphic lenses on a SmallHD or Atomos monitor, just vertically instead of horizontally.

When I make content to run in IMAX I like to do Flat at 400mbps. Flat fills up about 80% of the height of the screen. 400mbps is overkill and doesn't work on most servers, but it does just fine on our IMAX and when your picture is 80ft wide you want it to look the very best it possibly can.

Audio wise it will default to 5.1 or 7.1 on a non-IMAX DCP, but you can add automation cues to the show playlist or manual change sources to get Immersive Audio. The 16 Channel option in DCP-O-Matic works for this, though IMAX's channel assignment is different. It's basically the same for 7.1 (L,R,C,LFE,RL,RR,HI,VI,SL,SR) except it replaces LFE channel 4 with a "voice of god" center ceiling channel. Channels 11-14 make up the Front L/R and Rear L/R ceilings, and a crossover sends low frequencies in place of a LFE channel.

So TL;DR unless you spend the money to have IMAX POST author your content, it can't be dual projector or 1.43 aspect ratio, but will run just fine in whatever normal DCI spec.

[scorpio81]

Hi! I'd like to add some hopefully useful info to this topic.
I think it's best to create full container DCP with an image filling it completely. IMAX has no problem projecting these DCPs.
I had problems projecting encrypted 4K DCP, no matter what I did. But no problems with encrypted 2K or unencrypted 4K. So if you want encryption then make a short test DCP first.
I spoke once to an IMAX service technician and technically it is possible to project non-IMAX content with two projectors but he never revealed me how to do it. I guess it's something to do with an Image Enhancer settings.
The title card saying "This Is Not The IMAX Experience" is displayed only for FTR DCP longer than 30 minutes (if I remember it correctly from IMAX manuals). So it is possible to create, say, TST DCP to avoid this card. But I never did it myself so it's better to try.