Aspect ratios can be a bit confusing when you start a movie project that will end up in a cinema. Do you used the HD convention (1920×1080 or aspect 1.78)? The 2K convention (2048×1080 or 1.90)? Some people talk about ‘scope’, what’s that? Well, let me get that straight for you:
Cinema ‘flat’ or 35mm widescreen = 1.85
I am mainly speaking from my experience with European cinema, but movies here are either ‘flat’ or ‘scope’. The first is the oldest standard of the two. The aspect ratio for ‘flat’ is 1.85: the width is 1.85 times the height. Before that, there used to be 4:3 and 5:3 movies but you won’t find those anymore. Compared to those dimensions 1.85 is indeed ‘wide’.
Cinema ‘scope’ or Panavision = 2.39
This is the super widescreen format used in most blockbusters and Hollywood movies. It’s much wider and gives a better cinema immersion feeling, if you believe the directors. It was originally an anamorphic format (the actual film was still 1.85 or 4:3 but the image was stretched horizontally to fill the whole screen), but this is no longer the case in digital cinema. See below for the pixel dimensions of the digital scope.
HD = TV standard
HD (1920×1080) is a high-definition TV standard. If your movie project is going to be shown only on TV, this might be the best option. Most of the cinema commercials have this dimension too, partly due to the fact that a lot of commercials were originally created for TV, and cinema advertisers want to keep the same aspect ratio for all clips. Are you shooting a commercial or a trailer that will be shown together with ‘flat’ material? No problem for HD. Will it run before ‘scope’ material? Then you might be in trouble using HD (read on).
2K = artificial standard
The reason for making 2K (2048×1080) slightly bigger than HD seems to have little other reason than that it is a bit bigger and that they need a catchy name. Cinema content is almost never 2048 x 1080 sized, but it is almost always distributed in a 2K (or 4K) ‘envelope’. What does that mean:
- cinema ‘flat’ is encoded as 1998 x 1080 frames: aspect ratio 1.85 and fits inside the 2K frame. The frames can be just that size, or black bars are added left & right to get to the full 2K size (‘pillar boxed’).
- cinema ‘scope’ is encoded as 2048 x 858 frames: aspect ratio 2.39 and fits inside the 2K frame. The frames can be just that size, or black bars are added top & bottom to get to the full 2K size (‘letter boxed’).
Screen aspect ratio
Keep in mind that the cinema screens also come in flat and scope. Most modern cinemas over here in Europe install a scope screen (2.39). They use one lens setting for ‘flat’ content (they need to fit the full 1080 height on the screen – so they get black space on the left and right) and another one for ‘scope’ content (they zoom in more, because they want to fill the full width and they know only 858 pixels of the height are used). This operation of zooming in can be automated, but requires at least 5-10 seconds.
So the whole preshow of the ‘scope’ movie will typically split in a a ‘flat’ part in the beginning (commercials, branded content), a lens switch and a ‘scope’ part (trailers & feauture film). If your movie is mastered on ‘scope’ ratio, and it is shown in the ‘flat’ part, it will not fill the whole screen, but will be both letter-boxed (black above and below) and pillar-boxed (black left & right). It will run in a big black frame. Just so you know.
Your HDSLR will typically shoot in Full HD format. The conversion to flat or scope will be done during editing. Some DoP’s will put some gaffer tape on the preview screen to see only the scope part, since the rest will be cut away later anyway.