Articles and whitepapers

Creating a True Cinemascope Experience at Home (19/4/2006)

By Alan Roser, SIM2

Ever since films have been seen on TV via video, DVD, cable and satellite, one discussion always rages on, and that is about aspect ratios and the dreaded black bars.

This discussion usually falls into two camps, namely those who want a full screen - they have paid for their DVD or TV license and want the full picture, and those who wish to see the film as the director intended, as it was presented in the cinema - in glorious widescreen.

I must confess that I am in the latter camp - I love to see a film on the big screen in a movie theatre or on a projector in the comfort of my home, and with the recent arrival of anamorphic lenses for home theatre projectors, we can now experience the wonder of Cinemascope at home.

Aspect ratios

Before I explain the purpose of an anamorphic lens, it may be useful to have a brief history lesson on film and TV aspect ratios, and a basic understanding on what goes on when a film is projected in a cinema.

At the beginning of the motion picture era, a basic specification was set by the Academy of Motion Picture Arts and Sciences to have a picture aspect ratio of 1.37:1. For those who are mathematically challenged like me, it simply means that the image is 1.37 times wider than it is high. In fact the picture was almost square, and that was the shape of cinema screens from the late 1920's to 1953 when it all changed. So, if you are avidly looking for that widescreen version of 'Gone with the Wind', I'm afraid you are out of luck as it doesn't exist!

By the 1950's, the death of cinema was widely debated with the arrival of television. Interestingly, the shape of the TV tube was set to a similar shape as a cinema screen - this time with an aspect ratio of 1.33.1 or, as we most often refer to it, 4:3. This meant when a film was shown on TV, you saw it exactly as it was in the cinema. Dèja vu anyone?

The arrival of Cinemascope

With cinema audiences falling as a result of the arrival of TV, studio bosses needed something that would attract the paying public back into theatres - and the widescreen format was born, several of which were launched. Names such as VistaVision and Cinerama featured in the opening credits, but it was Cinemascope - developed by Twentieth Century Fox - which is the most famous, and in essence, remains to this day as the widescreen format of choice, although the name of Cinemascope is no longer officially used.

The clever thing about Cinemascope was that the 35mm film print remained generally unchanged. All that was needed was a special lens on the camera that would squash a wide shot onto a 35mm print (see Figure 1) and the appropriate lens fitted to the film projector to restore the image to the original widescreen ratio as shot by the director (see Figure 2). This process is called 'anamorphic', meaning deliberate distortion.

Figure 1 - A 35mm print image squashed by a Anamorphic lens attached to the camera.

Figure 2 - Image as seen in the cinema - an anamorphic lens is fitted to the film projector, which horizontally stretches the image to the correct shape.

During the 50's and 60's screens became wider - in some instances up to 2.7 times wider than they were high. It was not until the 70's that the film industry settled on a screen aspect ratio commonly know as 2.35:1 - the Cinemascope aspect ratio. The film studios had achieved what they wanted - to get customers back into the cinema to see the big epics up where they belong, on the big, wide, silver screen.

Pan and scan

Now, of course, comes the problem of showing a film image which is basically in the shape of a rectangle on a TV screen which is almost square - they don't fit - so the process of 'pan and scan' was born. This involves an operator controlling what portion of the film frame can be seen on a TV screen. Figure 3 shows what part of the 2.35:1 film frame is being seen on a TV and what is being missed. As you can see, over 40% of the film frame is missing - a good reason why film enthusiasts do not like pan and scan. However, showing a rectangular film frame as a narrow strip across a 4:3 screen was considered even worse. History lesson over!

 
Figure 3 - Example of pan and scan and what you do not see on a 4:3 TV compared to the widescreen presentation. (Copyright Universal Home Video - used for illustrative purposes only. No copyright infringement is intended or should be inferred).

Widescreen in the home cinema

How does all of this affect your home cinema? As you may be aware, over 60% of films made today are in the aspect ratio of 2.35:1, but even though our new TV screens and projectors have become wider and rectangular, they still do not match the shape of the big blockbuster, and we still have part of our valuable picture space taken up by black bars.

To get that Cinemascope experience on our screen, we need three things:

1. A home theatre with a screen that is in the shape of 2.35:1. Remember, this means it is 2.35 times wider than it is high. Such screens by Da-lite, Stewart Filmscreen and others for example, have dual masking systems that change the shape of the screen automatically between 1.78:1 and 2.35:1.

2. A digital projector that has multiple aspect ratio control, such as the SIM2 range of DLP Home Theatre projectors. The reason this function is needed is straightforward - we have to stretch the image, as shown in Figure 4, vertically so we lose the black bars at the top and bottom of the screen, and everything becomes tall and thin as in Figure 5.

Figure 4 - Same frame as seen on DVD on a 16:9 display.

Figure 5 - The image is now stretched vertically by the projector, the shape of the frame is now the same as the original print.

3. We need an anamorphic lens, as in Figure 6, to be introduced into the light path of the projector as in Figure 7. This will stretch the image horizontally by the same proportion that the image was stretched vertically, so that the original frame shape is restored, as in Figure 8.

Figure 6 - The IscoOptics Isco III anamorphic lens attachment.

Figure 7 - The IscoOptics Isco II mounted in front of a SIM2 C3X projector.

Figure 8 - By introducing the anamorphic lens the image is horizontally stretched to restore the correct aspect ratio. The image is now wider but without the black bars. The 16:9 screen is indicated by the dotted line. Therefore a wider screen is now required.

This form of projection is sometimes known as 'Constant Height Projection' which means that the height of the image remains fixed between the widescreen format of 2.35:1 and normal film viewing of 16:9 material. Only the width of the image changes.

Conclusion

By losing the black bars on the image we gain more light from the display and it also means that we use more pixels to generate the image, delivering even better picture quality and enhancing the viewing experience further. Of course, the quality of the lens is of great importance, which is why SIM2 for example, promotes anamorphic lenses from IscoOptics Germany, a company that has been manufacturing camera and film lenses for over 60 years.

So, for that real home Cinemascope experience invest in some 50-year-old technology and treat yourself to an anamorphic lens. Home cinema just gets better - and wider!

Alan Roser is the Managing Director of SIM2, leading manufacturer of home theatre projectors based on DLP technology.

www.sim2.co.uk