Making A DCP: Aspect Ratio & Frame Size

Aspect ratio is a fancy term for the width-to-height ratio of an image. This ratio is important for a variety of reasons, but when it comes to projecting your film correctly in a cinema, understanding both what it is, and how it’s used is paramount. Improperly projected aspect ratios can show up in the theater as un-intentionally cropped images or strange letter/pillarbox combinations. When this happens, the mis-projected image can become distracting, even impossible to watch.

Aspect ratios can either be written as a fraction like 16:9 (also commonly seen as 16x9), or as a decimal which is just the fraction divided out. In this example 16:9 would become 1.78:1 (which is still written as a ratio) or abbreviated to just “1.78.” In the video / television world, you’ll see aspect ratios written as fractions while in the cinema world you’ll see aspect ratios often written as decimals.

While there have been a ton of popular aspect ratios used throughout the history of cinema, the two most used in digital cinema are 1.85, also referred to as “Flat”, and 2.39 also called “Scope”. When creating the standards for digital cinema, engineers created when they called “containers” and assigned specific frame sizes to each container.

You’ll notice that there’s a third size listed called “Full Container” which should never be used for delivery of a film. Why? Digital cinema equipment is programmed with ‘macros’ or presets which set up the projector and the screen masking (black curtains) for projecting either the Flat container or the Scope container. When a projectionist receives a film, they only have these two modes they can use to set up their theater. Also, there aren’t screens installed in theaters that have an aspect ratio of 1.9:1.

So what does this mean for your film? Aspect ratio is often an artistic choice, and one that is determined as early as pre-production. No matter the aspect ratio you’ve chosen, at the end of the day it will be placed into one of the two standard containers for delivery to cinemas. This doesn't mean that you have to shoot your film at one of these aspect ratios. You will, however, need either letter-box or pillar-box your film to fit. Projecting light onto a reflective screen is a fundamentally different method of viewing than watching something on a television or computer screen because of the optical factor (lens zoom) that is present in the cinema. Here’s an interesting series of images that show Flat vs Scope presentation in cinema.

If the active picture area of your film is different than the one of the standard containers, a letter-box (black bars above and below the active picture area) or pillar-box (black bars to the left and right of the active picture area) can be added to your picture area to fit a flat or scope container.

Here’s a list of commonly used aspect ratios and associated containers.

By understanding film containers and frame sizes for digital cinema, you will be able to plan appropriately during pre and post production for final cinema delivery.

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