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Film Projection Perfection
The Fabric of Magic, Part 2
Mark Trompeteler FBKS
discusses today’s projection of 5perf/70mm and 15perf/70mm film with Michael Ford of London’s BFI IMAX cinema.

The 70mm Newsletter
Written and photographed by: Mark Trompeteler, FBKS meets with Michael Ford of London’s BFI IMAX cinemaDate: 16.03.2024
Michael Ford

As expected, the 2023 Summer release of Christopher Nolan’s film "Oppenheimer" not only generated much excitement in the cinema industry as a whole, but also very much amongst worldwide 70mm fans.

• Go to gallery Film Projection Perfection
• Go to The Basics of The Rolling Loop IMAX Projector

As was widely known at the time there were 118 5perf/70mm prints, and 30 15perf/70mm prints struck by the only film laboratory in the world capable of producing both formats of 70mm prints, FotoKem in Los Angeles. North America dominated the 15perf/70mm engagements with 19 in the USA and 6 in Canada. The remaining engagements were 1 in Australia, 1 in the Czech Republic and 3 in the UK.

There are less than 60 70mm analogue IMAX projectors globally and I was very excited to see “Oppenheimer” at my local South London iconic BFI IMAX cinema, which houses one of those projectors. The cinema went through a major five week upgrade between October and November 2022. Its 493 steeply raked plush new seats face a brand new screen which is a staggering 65 feet high and 85 feet wide. The refurbishment also included IMAX’s new 12-channel sound technology, with new side and overhead channels that deliver greater dynamic range and precision for the ultimate in audio immersion. Also alongside the rare and classic IMAX analogue projector is a new 4K Laser IMAX projector.

Since launching 23 years ago in 1999, the BFI IMAX has become one of the most successful IMAX cinemas in the world, welcoming an average of 300,000 visitors each year. The summer 2023 engagement of “Oppenheimer” here was a phenomenal success. For several weeks the film screened every four hours, 24 hours a day, for seven days per week with performances fully selling out a week or two in advance. I saw the print after it had been screened about some 70 to 80 times. The performance was one of the very best cinematic audio visual experiences I can remember for a very long time.
More in 70mm reading:

The Fabric of Magic:
Part 1 – The Kodak View

The Basics of The Rolling Loop IMAX Projector

Imax Sound System

Interstellaring in London

Anamorphic Weekend in London

in70mm.com's Library

Presented on the big screen in 7OMM

Peripheral Vision, Scopes, Dimensions and Panoramas

L-R Century, Christie 2K, IMAX & IMAX 4K Projectors

Many readers may well know Michael Ford, the technical manager/projectionist. He has had some 45 years experience working for Odeon cinemas and Michael and his team won the Cinema Technology Community’s “Cinema Team of the Year” Award in 2017. Michael also featured in an article entitled “Meeting the BFI’s Greatest Showman” in the 2018 winter edition of the CTC-IMIS “Cinema Technology” magazine.

He has the benefit of having a dual format conventional 35mm / 5perf/70mm Century Projector, a 15perf/70mm GT IMAX projector, a 2K Digital Christie projector and a 4K Single Laser IMAX projector all alongside one another in the projection room. The three quarter tonne COLA single laser Digital IMAX projector is still relatively new. This single laser version, not being able to completely fill the full height of the screen, which the dual version can, was a comprise that was made as part of the Autumn 2022 installation. The increased size of the dual laser projector would have compromised the positions and capability of the other existing projectors. The COLA laser also has higher specifications for 3D playback as it can project high frame rate 60Hz 3D in 4K with the dual laser only being able to do this in 2K.

The cinema has a Rosetta Bridge Theatre Management System with 9TB of storage, a Doremi server with 2TB of storage, and the IMAX server has 3TB. An MPS LanSat connection is in development with the BFI Vaults in the nearby BFI Southbank complex.
BFI IMAX Auditorium from Projection Room

That magic of the fabric of 65mm/70mm film is exemplified by the amazing qualities of 15 perf/70mm film and its rare projectors. As well as the expertise of Michael and his team, (and someone called Nolan, and his team) - this is what made the screening of “Oppenheimer” I attended, so very special.

It is often quoted that 35mm film has a digital equivalent resolution of between 5K to 6K. Scaling up in proportions, gives 5perf/65mm film a digital equivalence in the region of 12K resolution. Currently commentators have been rating 15perf/65mm IMAX film, at a digital equivalent resolution of between 16 to 18K.

The fabulous quality of 15perf/70mm film is maintained in the eyes of the audience by the design of the IMAX projector. As Michael pointed out to me, there are only two sets of sprockets, one at the input side and one at the output side. Physically pulling down of the film like in a conventional film projector is done away with. This physical contact with the film in transporting it past the projection aperture contributes to wear on the film and increases the possibility of dust, scratches and tears. With an IMAX projector rolling loops of the film are involved in feeding the film into the projector and around a large ring or rotor. Gaps at regular intervals form the loops that feed the film along, with the loop growing as it approaches the projection aperture. Once there the frame is held in place for the fraction of a second it needs to be held. The film is held in place briefly by a vacuum with pins engaging the sprocket holes to ensure the frame is in the exact correct position. The frame is illuminated before being pushed away. The perforations in the film are used for positioning the film correctly for the aperture. Hence the IMAX projection process involves far less wear on the film which helps maintain its fabulous pristine quality on screen.
Twin Lenses & Twin Rotors IMAX Projector Front

The BFI’s 15/70 GT IMAX projector has two rotors, mounted one above the other, complemented by two lenses for showing 3D films. Each rotor is fed by a different platter of film - the two slightly different right and left eye reels of film. The two 15,000-watt xenon lamps create so much heat that the lamphouse above the rotors must be water-cooled – this is achieved by cooling equipment located outside the projection room.

Michael is the perfect person to discuss the exhibition perfection that both formats of 70mm can yield – even in a cinematic world so dominated by digital projection. As well as very kindly showing me around the fabulous projection room He spent some time discussing the projection of 70mm IMAX with me.

Mark Trompeteler: Michael readers will very much be familiar with the conventional type of 5perf/70mm projector. We all know how big 15perf/70mm film is and the huge size of the frame and how it runs horizontally though the IMAX projector. Could you outline the key things or innovations of the analogue IMAX projector that help contribute to the fabulous high quality experience that IMAX film is on the screen.

Michael Ford: Hi Mark yes of course, The projector uses the Rolling Loop system, that is incredibly gentle to film, this and the air jets that help the film through the projector make the projector film transport very smooth.

The vacuum that holds the film against the rear of lens on the Field Flattener along with the registration pins make for an incredibly stable picture on such a large screen.
Detailed Cleaning, Maintenance & Servicing Schedule

MT: How reliable is the IMAX projector? What type and level of maintenance from you does it require? When, if ever, have you had to contact IMAX as regards any maintenance, repair or refurbishment issues?

MF: Depending on use, the projector is serviced twice a year, this involves replacement of Cam bearings, lens mount alignment, projector timing, vacuum bag clean / replacement.

From a daily maintenance point of view after each show, all rollers are cleaned, projector Rotor is cleaned with wipes and alcohol and blown out with compressed air. The field flattener is cleaned with alcohol to remove any dust from the previous show, then a small dab of Rainx is put on and buffed to clean the glass until perfectly clean, also it is dusted with compressed air. Wiper bars are changed as required and checked they are making good contact with the field flattener.

MT: The image on the screen of the performance I have just seen, knowing the print had been shown for some 70-80 times, was immaculate. I barely caught sight, for a fraction of a second, of one or two tiny flecks of dust on the print in the entire three hours. It was immaculate. Obviously the huge size of the frame helps. What precautions over and above conventional film handling, if any, do 15perf/70mm prints require – are things easier with their print handling or more difficult or the same?

MF: We try and keep the Booth as clean as we can to keep dust down, so we vacuum the floor twice a day, doing this with Kodak PTR rollers helps a lot. Like all film IMAX 15/70 requires respect and care when handling it. If we do not run a print for a period of time, before its next showing we will do a cleaning run in the morning, running it through the projector with field flattener turned off to pick up any dust.
"Oppenheimer" Print on Platter

MT: I understand IMAX film platters were enlarged in order to cope with the running time of “Interstellar” and again now to cope with the running time of “Oppenheimer”? The whole delivery and making up of this 15perf print was quite an undertaking I understand?

MF: Yes it was a challenge for the team, the print was held up in customs so we had two days to assemble 53 reels of film before a rehearsal.

MT: Can you have more than one 15perf print fully made up on a platter ever? Is it possible to have two or three fully made up 15perf prints in the projection room available to screen? Or do you have only one print made up and have to show it through a season then have to break it down? Breaking down a 15perf print and preparing it for delivery to elsewhere must be somewhat of a procedure too?

MF: Yes we have 5 decks and can have three full size films made up on to the QTRU (Platter) and one 2D documentary, this still gives us a take up plate. Deck 2 to 5 can handle full length films, and deck 1 60 min of film. We have all of Christopher Nolan’s IMAX films in the booth made up and ready to show, 8 films in total.

MT: It is generally reported that the 15perf/70mm frame yields the best quality cinema experience ever. At 3-4 times the size of a 5perf/70mm frame and between 8-10 times the size of a conventional 35mm frame Christopher Nolan has been quoted as saying …

“the highest quality imaging format ever devised – it gives you an incredible sense of immersion in the image. The clarity, the crispness – it is the gold standard.”

You are in a rare position where you have so much experience in projecting from this box 35mm, 5perf/70mm, 15perf/70mm, IMAX 2K Xenon, and 4K IMAX Single laser. From your viewpoint, in terms of cinematic experience, how would you rate and compare the differing format experiences you provide to the audience and why?

MF: Very interesting question, The Technology itself is nothing without a good story, and when it is done right any format can capture your imagination, every format has its place, and it is about trying to make each format look as good as we can. IMAX 15/70mm is truly an epic format that immerses you to a level unlike any other when used to tell a story like “Oppenheimer”. Digital is good because it allows movies to be made on lower budgets and develop skills, and you never know if the person who makes films at college on Digital then wants to shoot on film later on.

Oppenheimer Print and Feed Rollers

MT: Nolan shoots his films with a variety of format cameras. When he switches to the full frame 15perf/70mm 1.43:1 aspect ratio on such a huge screen it is incredibly special. Do you, or your colleagues in the cinema, ever get any feedback from the audience about the often frequent changes in aspect ratio within a Nolan 15perf print? Do the frequent changes within such a print present any challenges to you?

MF: We don’t normally get feedback on this unless the movie has fast cuts between ratios that can be jarring to the audience.

MT: It must be incredibly satisfying for you and your team to be giving your audience that amazing 15perf/70m experience during the run of something like “Oppenheimer”, knowing you are playing to sold our houses 24 hours a day and knowing some people are flying in from across Europe to see the film here. What was it like for you and the team?

MF: It was a privilege for us to run, we had loads of people asking for a tour of the Booth to see the print and we try as much as possible to book them in for a look around and give them a piece of 15perf/70mm film.

MT: The UK is a small country and is fortunate in having three 15perf cinemas – do you keep in regular touch with your colleagues at The Science Museum and Manchester Printworks? About what issues?

MF: We do stay in contact with the London Science Museum, for any issues or just a catch up.

MT: Michael I wonder if you’d like to say anything about the experience of or any aspects of projecting both 5perf and 15 perf/70mm film?

MF: There is something very special about 70mm, to stand by the projector and hear it working and watching the stunning images it projects to an audience and think how very lucky I am to have a job like this.

MT: Thanks Michael for sparing the time to answer a few questions.
BFI IMAX on Waterloo Roundabout

Any visit for whatever purposes to the BFI Imax should not ignore what an amazing cinema it is in itself. Fans of 70mm know that a premier film format deserves a premier venue. Designed by Bryan Avery of Avery Associates, it won several architectural design awards after it was built back in 1999. It is a great feat of engineering in its ability to insulate itself from adverse conditions below it, and in insulating itself from the noisy traffic around it. An underground line runs just 4.5 metres below it. Supporting pile foundations had to be built down between the tunnels with a substantial concrete slab constructed over them to support the building. In addition the auditorium rests on springs to help isolate it from the vibrations of underground trains running underneath it. The external circular facade features a secondary glazed curtain wall and thick insulation to prevent Waterloo traffic roundabout noises coming into the auditorium and the worrying sounds of atomic explosions leaking out. The cinema features a DMX lighting system which allows the team to alter the colour scheme of the entire foyer, some of the public areas and the auditorium to suit the movie being shown. When I attended, the dominant scheme was all red and orange (flame, energy and explosion.) No doubt for “Avatar: The Way of Water” the colour scheme would have been very different.

If you want to see how brilliant 65mm/70mm film can look on a screen – the BFI IMAX is a very good place to start.

• Go to 65/70mm Film: The Fabric of Magic: Film Projection Perfection
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Updated 16-03-24