Does Sensor Size Matter?

INTRODUCTION

The sensor or film plane of a camera is the area that light hits to record an image. The size of this area can vary a lot depending on the camera, with each sensor size or format having a subtly different look. 

Since there are loads of different cameras with loads of different formats and sensor sizes out there to choose from, in this video I’ll try to simplify it a bit by going over the five most common motion picture formats and discussing the effect that different sensor sizes have on an image.   

5 MOTION PICTURE FORMATS

The size of a video camera's film plane or sensor ranges all the way from the minuscule one third inch sensor found in smartphones or old camcorders up to the massive 70x52mm 15-perf Imax film negative. But, rather than going over every single sensor in existence, I’m going to take a look at five formats which are far and above the most popular sizes used in film production today and have been standardised throughout film history.

While there are smaller sizes like 8mm film or sizes in between like the Blackmagic 4K’s four third sensor, these sizes are used far less frequently in professional film production and are an outlier rather than a standard. I’ll also only be looking at video formats so won’t be going over any photographic image sizes such as 6x6 medium format.

The smallest regularly used format is Super 16. The film’s smaller size of around 7.4 by 12.5mm makes it a cheaper option than the larger gauge 35mm, as less physical film stock is required. 

Due to this it was often used in the past to capture lower budget productions. Now that digital has overtaken film, Super 16 is mainly chosen for its optical capabilities. Its lower resolution look and prominent film grain means that it is often used today to evoke a rough, documentary-esque feeling of nostalgia.

Some digital cameras, such as the original Blackmagic Pocket Cinema Camera have a sensor that covers a similar area to Super 16 and cameras such as the Arri Alexa Mini have specialised recording modes which only samples a Super 16 size area of the sensor.

Moving up, the next, and by far the most common format is Super 35. This format is based on the size of 35mm motion picture film that covers an approximate area of 21.9 by 18.6mm. 35mm refers to the total width of the frame, including the perforated edges on either side of the negative area.

Depending on the budget, aspect ratio, and lenses different amounts of horizontal space, measured in perforations, can be shot. The frame can be cropped to use less film stock or to extract a widescreen image when using spherical lenses. Shooting with anamorphic lenses, that optically squeeze the image, requires using the entire area of the negative or sensor and then de-squeezing the image at a later stage to get to a 2.39:1 aspect ratio. 

Many digital cinema camera sensors are modelled on this size, with some minor size variations depending on the camera, such as the Arri Alexa Mini, the Red Dragon S35 and the Sony F65. Since this format is the most popular in cinema, most cinema lenses are designed to cover a Super 35 size sensor. Meaning this format has the widest selection of cinema glass available on the market.

Stepping up from 35mm we get to what is called a large format or a full-frame sensor. This size is modelled on still photography DSLR cameras with a 35mm image sensor format, such as the Canon 5D that is larger than Super 35. It’s also around the same size as 8-perf Vista Vision film. 

Although digital sensors differ a bit depending on the camera, it is usually about 36 by 24mm. Some cameras with this sensor size include the Alexa LF, the Sony Venice and the Canon C700 FF. 

This large format is a middle ground between Super 35 and the next format up - 65mm.   

Originally, this format was based on using 65mm gauge film which was 3.5 times as large as standard 35mm, and measured 52.6 by 23mm using 5 vertical perforations with a widescreen aspect ratio of 2.2:1. The Alexa 65 has a digital sensor that matches 65mm film and is a viable digital version of this format.

Finally, the largest possible motion picture format that you can shoot is Imax film. With an enormous 15 perforations, an Imax frame covers a 70.4 by 52.6mm image area. 

Due to its enormous negative size and the large, specialised cameras required to shoot it, this format is prohibitively expensive and out of the budget range of most productions. But, it has seen a bit of a resurgence in recent years on high budget blockbusters from directors such as Christopher Nolan who champion the super high fidelity film format.    

THE EFFECTS OF SENSOR SIZES

With these five formats in mind, let’s examine some of the effects and differences between them. There are a few things that choosing a format or sensor size affects.

The most noticeable optical effect is that different formats have different fields of view. What this means is that if you put the same 35mm lens on a Super 16, Super 35 and a large format sensor camera, the smaller the sensor is the tighter the image that is recorded will appear. 

So the field of view on a large format camera will be much wider than on a Super 16 camera which is tighter. Since the field of view is wider, larger formats also have a different feeling of depth and perspective.

Because of this difference, the sensor determines the range of focal length lenses that need to be used on the camera. To compensate for the field of view differences, smaller formats like Super 16 need to use wider angle lenses to get to an image that sees the same amount of information, while larger formats need to use longer lenses for that same frame.

For example, to get the same field of view from a 35mm lens on a Super 35 sensor, a Super 16 camera needs to use a 17.5mm focal length and a large format, full-frame camera needs to use a 50mm focal length.

Since focal lengths affect the depth of field an image has, this is another effect of different formats. Longer focal lengths have a very shallow depth of field or area of the image which is in focus. So full-frame cameras that use longer focal lengths will therefore have a shallower depth of field. This means that the larger the format, the more the background will be out of focus and the more the subject will be separated from the background.

This is helpful for creating a greater feeling of depth for wide shots which people often perceive as looking more ‘cinematic’.

One negative effect of this is that the job of the 1st AC to keep the focus consistently sharp becomes far more difficult. For this reason smaller formats such as Super 16 are far more forgivable to focus pullers as they have a deeper depth of field where more of the image is in focus and therefore the margin for error is not as harsh.

The grain and resolution that an image has is also affected by the size of the format. The smaller the format is, the more noticeable the grain or noise texture will usually be, and the larger the sensor is the finer the grain will appear and the greater clarity and resolution it often has.

Sometimes cinematographers deliberately shoot smaller gauge formats like Super 16 to create a more textured image, while others prefer larger formats like 65mm for it’s super clean, sharp, low noise look.

So those are the main optical effects of choosing a format.

Smaller formats require wider focal lengths, have a deep depth of field, have more grain and will overall feel like they are a bit flatter.

Larger formats require longer focal lengths, have a shallower depth of field, less grain, greater resolution and clarity and overall have a more three-dimensional look with an increased feeling of depth.

There are also the all-important practical implications to be considered. Generally speaking the larger the format, the larger the form factor of the camera will be to house it and the more expensive it is to shoot on. 

This calculation may be different when comparing the costs of digital and film, but when comparing all the digital formats, renting the cameras and lenses for 65mm will be more expensive than a Super 35 camera. Likewise, when comparing film formats 16mm is vastly cheaper than Imax.

So broadly speaking, smaller formats tend to be more budget friendly and come in a smaller housed package. 

DOES SENSOR SIZE MATTER?

Coming back to the question of whether sensor size matters, I don’t think any one sensor is necessarily better than another. But the effects that they produce are certainly different. 

Filmmakers that want an image that immerses an audience in a crystal clear, highly detailed, wide vista with a shallow depth of field will probably elect to shoot on a larger format.

Whereas those who require a more textural, nostalgic or rougher feeling photography with less separation between the subject and the background may be drawn to smaller gauge formats.

As always, the choice of what gear is most suitable comes down to the needs of the project and the type of cinematic tone and photographic style you are trying to capture.