Use our Aspect Ratio Calculator below to find your required dimensions and read on to learn how the more common ratios became standardised in the film and TV industries.
Aspect Ratio Calculator
Aspect Ratio Demystified
Digital video is one of those technical areas where jargon proliferates. Sometimes it seems like the film and video experts are competing with the computer experts to see who can come up with the most baffling technobabble.
When we talk about the aspect ratio of a film or a video, we are simply talking about the shape of the image. When an aspect ratio is written down, it is normally written in the form width:height, where width and height are numbers that tell us how many units wide an image is for a particular number of units high. Common ratios are 4:3 and 16:9, and you will also see figures like 2.33:1 or 1.85:1. Occasionally, you might see aspect ratio described as a single number – if you do, the single number refers to the width, and the height is 1. For example, 4:3 could be written as 1.33:1 or simply, 1.33.
Terms like widescreen, Cinemascope and Academy Ratio describe quite specific shapes, but aspect ratio also comes into play when we use terms like Standard Definition or HDTV because they incorporate a screen shape as well as resolution.
In the early years of cinematography there was little standardisation and many fiercely protected patents but, by the end of the 19th Century, there was a bigger appetite for standardisation as the industry became more commercialised. In August 1889, Thomas Edison’s assistant, William Dickson, placed an order for roll film from Eastman Kodak and with slight refinements and modifications, the format that he specified is still in use today.
Dickson was influenced both by the dimensions of the commonly available 35 mm still photography film, and his own idea of the aesthetics of shot composition. He specified an aspect ratio of approximately 4:3 (width:height) and by 1917, the newly formed Society of Motion Picture Engineers, adopted Dickson’s format which subsequently became the predominant format used throughout the 20th Century.
There were two big advances in cinema technology during the first half of the 20th Century that would affect the aspect ratio of the projected images in cinemas. The first one was the introduction of sound.
As sound was developed, soundtracks were either recorded separately onto discs that were then synchronised with the projection in the cinema; or the soundtrack was recorded optically on the film so that synchronisation was automatic. Optical soundtracks became more widely used, because of the convenience and accuracy of the synchronised reproduction, but the inventors of the early sound formats had to tweak the aspect ratio of the image to make space for the soundtrack on the film. The aspect ratio was changed from 1:33:1 to 1.15:1, making the image area slightly narrower and therefore leaving room for the optical soundtrack.
This gave cinemas a bit of a headache because their projection screens were all designed for the wider 1.33:1 image. Consequently, cinemas started to use metal plates with a hole cut to correspond to the original 1:33 aspect ratio masking off the top and bottom of the image. When the projector lens was adjusted, the cinemas could fill their screens again. The studios didn’t like this much and eventually, the situation was resolved with the introduction of the Academy Ratio.
The Academy of Motion Picture Arts and Sciences (hence Academy Ratio) introduced a new film format which defined new frame dimensions that didn’t occupy the area in which the soundtrack was recorded. By slightly increasing the height of the black gap between frames, they changed the aspect ratio to 1.37:1 which was so close to Dickson’s original 1.33:1 ratio that cinemas did not need to modify their projection screens. Although the new frame size was physically smaller than before, improvements in film technology meant that there was no noticeable loss of quality.
Academy ratio is rarely used in modern filmmaking, but there are notable exceptions. The film The Grand Budapest Hotel, directed by Wes Anderson used three different aspect ratios to represent three different periods of time.
The second technological change that affected the aspect ratio of film was the introduction of various widescreen formats from the middle of the 1950’s. Television was beginning to compete strongly with cinemas and the film industry needed to find ways to differentiate their offerings from TV.
Apart from an early diversion, television broadcast standards originally set the aspect ratio to 1.33:1. Of course, this makes plenty of sense, even ignoring any aesthetic considerations. Although many of the TV broadcasts originated from TV cameras, these were unwieldy devices, so if you wanted portability you had to use a film camera with a 1.33:1 aspect ratio and then convert from the film to television. It also helped that the movie industry could easily provide an enormous library of content to the broadcasters, as long as TV standards use the same aspect ratio as film.
Widescreen formats came about because the movie industry needed a new gimmick that TV could offer. Many widescreen formats needed multiple projectors and non-standard film formats but Cinemascope, the most successful, managed to use 35 mm wide film stock and a single projector. When Cinemascope film is shot, the camera is fitted with a lens that compresses the image horizontally onto a standard width 35mm film. If you look at a Cinemascope frame, the image is distorted so that everything is tall and narrow, but when the image is projected using a lens that stretches the image horizontally, normal proportions are restored and the projected image is much wider than usual.
The Cinemascope aspect ratio is approximately 2.55:1, much too wide to display on a standard TV, so the film studios were back in business. Of course, films were still licensed to broadcasters, but the conversion to TV now cropped a 1:33.1 section of the widescreen film. TV broadcasters could still get their content, but cinemagoers viewed a better version.
During the second half of the 20th Century, competing widescreen formats fell out of use, in favour of Cinemascope and its derivatives. A variety of different aspect ratios were used but by the late 1970s Hollywood had settled on 1.85:1; whilst Europe and Asia tended to use 1.66:1. The narrower 1.66:1 ratio increasingly fell out of use, even in France where it was chosen by respected Nouvelle Vague directors such as Jean-Luc Goddard. By the end of the 20th Century, 1.85:1 was the commonest aspect ratio used by film studios.
The adoption of 1.85:1 as the aspect ratio of choice for movies is no surprise when you realise that it is very close to the 16:9 ratio that has been defined for widescreen television standards. The 16:9 ratio was chosen by SMPTE in the early 1980s because it was close to an average between all the major widescreen cinema formats of the time, but convenience, and the importance of DVD, Blu-ray and TV distribution means that the film ratio closest to widescreen TV is the most commonly used.
Where does that leave us now?
Even though there are dozens of different aspect ratios that have been used over the years in film-making , if you want to display digital video or images derived from digital video content, then it’s very likely that your content will need to be shown in a 4:3 or 16:9 ratio, or even a mixture of both. It’s also very likely that your source material is already in a 4:3 or 16:9 ratio.
If you have content that is destined for cinema presentation, then you might need an aspect ratio that is even wider that 16:9. This is probably quite a rare occurrence as, very often with this type of material, the digital video version is converted to a 16:9 ratio.
We will look at the choices that you have to make about the aspect ratio you choose to display your content with, and how best to make all of your content work with your chosen display format in a future blog post.
If you want to know more about the subject, try this book: Moving Image Technology, by Leo Enticknap, published in 2005 by Wallflower Press.
Wikipedia has a couple of useful articles on film formats https://en.wikipedia.org/wiki/List_of_film_formats and film aspect ratios https://en.wikipedia.org/wiki/Aspect_ratio_(image).