Masking Configuration for 70mm Screens
The 70mm Newsletter
and Mike Taylor
screen with movable side masking (unidentified location).
Courtesy Mike Taylor / PPT Collection
As the 70mm format is physically larger than 35mm, it follows
that corresponding screen size should also be larger. Though
this may seem obvious, there are different ways of achieving
this in practice.
A common technique is to have the 2.21:1 aspect ratio of 70mm
share common width with 35mm 'Scope 2.39:1, and to lift the top
masking for 70mm.
Other cinemas have arranged the layout so that both the side
masking and the top masking open out for 70mm.
A movable top masking only configuration is appropriate for 70mm
where additional available screen width is limited.
The importance of screen masking generally should not be
underestimated or neglected, as it performs an important
technical function in enhancing the contrast of projected
images, in addition to the more commonly cited advantage of
providing a pleasing hard edge / border.
Many cinemas today, whether regular or large format, do not use
screen masking and this is poor practice.
Additionally, in order to maximise the impact of the film
experience, it is paramount that the presentation of the main
feature in 70mm is completely different to any previous
advertisements and/or trailers both in image resolution, sound
quality and screen width and height.
By using the same screen surface for advertisements and the main
feature, or even having the main feature using less screen
surface (the incorrect "common width" screen configuration), the
impact of cinema and its differences to home cinema are
Correct screen masking coupled with a good use of
curtain tabs can enhance a film
The 65/70mm Workshop has also previously put forward a design
for a multi-format, compound
curved screen that is intended to be correctly masked.
[With thanks to Ben Wales for his assistance]
in 70mm reading:
SCREEN MASKING FOR 70MM PRESENTATION
By Mike Taylor
screen with movable side & to/bottom masking. Imperial Bio, Copenhagen,
Denmark. Image by Thomas Hauerslev.
When Cinerama took the cinema world by storm in 1952 it introduced a new
form of cinema - The Wide Screen. Following on the heels of this
development, film companies came up with other processes so as not to be
outdone in the race to have wide screen for the majority of film goers,
and at the same time to try and slow down the mass medium of television.
Mike Todd - who had been in the forefront of Cinerama and later fell out
with the company - went on to develop his own system where "Everything
Came Out Of One Hole". This was Todd AO - the AO being his partner, the
American Optical Company.
As the 70mm format is physically larger than 35mm, it follows then that
the screen size should also be greater. To the outside observer this is
indeed obvious, and the screen therefore requires masking to achieve the
relevant picture ratio.
Kinds of Screen Frames
Todd-AO screen with movable side & to/bottom masking. 3 Falke Bio
(closed), Copenhagen, Denmark. Image by Thomas Hauerslev.
To accommodate 70mm and the other standard current ratios in 35mm using
the same screen, various types of screen frames have appeared over the
years taking into account the size and shape of the cinemas. Four types
have been in common use:
(1) Flat screen frame - free standing with stabilising rear braces.
(2) Flying screen frame - with extra strength to allow for suspended
(3) Roller screen
(4) Deep Curve screen frame
With the exception of the roller screen, the screen frames included the
masking system as an integral part of the frame. Built within a box-like
structure it carried all the guide rollers and cables linked to the
motor controllers and limits. In most cases, the screen would be curved.
For 70mm, the screen would be at its maximum with both top and side
masking facility. In smaller cinemas where 70mm was included, maybe only
side masking would operate. A fixed picture height being the norm for
This type of screen for 70mm is the exception, and is usually found in
specialised venues such as museums. A typical example is the
Pictureville Cinema at Bradford, part of the National Media Museum. The
screen only carries a fixed border top and bottom. The side masking
making use of the screen curtains, with a rigid edge and opening to the
Deep Curved Screens
These screens are usually found in the major cinemas or specialised
venues, and were the pioneers for such systems as Cinerama and
Cinemiracle with a 146 degree curve. Following the demise of these
systems, the deep curve almost disappeared but came to the fore in 1967
with the introduction of D-150 at the Odeon Marble Arch, London. This
time the curve was reduced to 120 degrees.
The masking system was again an integral part of the screen frame and
allowed for D-150 70mm 35mm (cinemascope and normal) and had both top
and side masking, making this the ultimate presentation system.
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