2.4.1: Film versus Digital

 

One of the first decisions a cinematographer must make is what medium she intends to use to record the images: a physical film stock or a digital sensor. While this is a highly technical decision, it is also an important aesthetic choice that will affect the overall look of the final image. Not only are there differences in the look of film versus digital recording generally, but there are also subtle distinctions in the various film stocks and manufacturers, as well as the different types of digital sensors that come with different camera systems. Let’s take each one in turn.

Good old-fashioned film stock has been around since the dawn of cinema, though it has evolved quite a bit since those early days. In the beginning, the strips of light-sensitive material were made from nitrate, a highly flammable material, which was not so great when it was whirring through a projector past a hot lamp. It’s one of the reasons many early films are lost to history. They simply burned up too easily. Today, film stock is made from a much sturdier plastic. And on that plastic is a gelatin coating containing thousands of microscopic grains of light-sensitive crystals called silver halide. When light hits those crystals, they darken, depending on the amount of light. (And if it’s a color film, there will be three separate layers of those crystals, one blue, one red, and one green.) A chemical bath enhances that reaction to light, rendering a negative image that can then be projected.

Once a cinematographer commits to this analog, chemical process, there are still a lot of decisions to make. First, they must choose a film gauge, that is, the size of the film stock. The film gauge is determined by measuring from corner to corner the individual frames that will be exposed to light. The standard film gauge in cinema today is 35mm, but sizes range from as small as 8mm all the way up to 70mm. And each size will render a different look, with more or less detail once enlarged. They must also decide how sensitive the film will be to light. Highly sensitive, or “fast” film stock, that is, a film that reacts quickly to relatively low levels of light, contains relatively large silver halide crystals (more surface area to absorb the light). The benefit is the ability to film at night or in other low-light situations. The drawback is a loss in resolution or detail in the image due to an increase in the crystals. Or grain. Less sensitive, or “slower” film stock produces a crisper image (due to the smaller crystals) but requires more light.

There are many other decisions to be made that may affect the final image – the manufacturer, black and white versus color, the developing process – but using the physical medium of film stock renders an image that many filmmakers claim has a more organic look, a difference you can almost feel more than see. And that comes at a price. Film stock must be purchased by the foot, forcing filmmakers to plan every shot carefully to avoid wasting material. (Of course, many filmmakers see this as a good thing). Not to mention the fact that you don’t really know what you have until you develop the film after a day of shooting. Or the fact that you have to assemble your final film by actually cutting and taping together physical strips of film. Or the fact that even if you choose to shoot on analog film stock, most of your audience is going to watch a digitized version in the multiplex or on their television, laptop or smartphone anyway.

For these and many other reasons, the good old-fashioned film has fallen somewhat out of fashion in favor of the flexibility of digital cinematography. Digital cinematography is identical in every way to analog film cinematography – same basic equipment, same need to control exposure, shape light, compose the image, etc. – with one important difference: the light passing through the lens hits a digital image sensor instead of a strip of plastic film. That sensor uses software to analyze and convert the light bouncing off its surface into a series of still images (just like film stock) that are recorded onto flash memory or an external hard drive.

The advantages should be obvious. First and foremost, there are almost no limits on how much you can record, especially as digital data storage becomes cheaper and cheaper. And since the sensor is controlled by software, you can adjust settings such as light sensitivity at the press of a button rather than changing out the film stock.

But there are still lots of decisions to be made. Just as there are various film gauges, digital sensors come in all shapes and sizes, and every camera manufacturer produces their own subtle variations. And while most of us could probably never tell the difference, cinematographers are very particular about the way a Canon sensor renders color differently from a Sony sensor or a RED sensor from an Arri sensor.

And then there’s the issue of resolution. The standard for “high definition” is an image measuring 1,920 pixels by 1,080 pixels, also known as 1080p (the “p” stands for progressive scan since the image is rendered line by line from top to bottom). Pixels are the smallest visible unit in a screen’s ability to produce an image. Think of them as analogous to those tiny silver halide crystals in film stock. 1,920 by 1,080 pixels is a lot of detail, but most digital cinema today is recorded at a much higher resolution of at least 4,096 pixels by 2,160 pixels, or 4K. And even that has become commonplace and somewhat outdated. In fact, you probably have a 4K camera in your pocket right now. It’s on your phone. As the technology improves, we’ll see 6K, 8K, and 10K become standard. All that information packed into every image renders an incredible amount of detail (and also eats up a lot of storage space). Detail most of us, frankly, will not be able to see with the naked eye.

But resolution isn’t the only factor that affects image clarity. Cinematographers can also manipulate the frame rate to render super-sharp imagery. For decades, the standard frame rate for cinema has been 24 frames per second. That produces a familiar, cinematic “look” to the finished film in part because of motion blur, the subtle blurring that occurs between still images passing at 24 fps. But film shot and projected at 48, 96, or even 120 frames per second renders an ultra-sharp image with almost no motion blur as our brains process far more detail between each individual frame. To be fair, this is possible with analog film stock, but it is impractical to shoot that much film stock at that high a rate. Digital cinematography gives filmmakers like Ang Lee (Billy Lynn’s Long Halftime Walk (2016), Gemini Man (2019)) and James Cameron (the Avatar series) the freedom to experiment with these higher frame rates combined with higher resolution sensors to produce images we literally have never seen before.