The digital sensor is quite amazing. Silicone wafers manufactured in such a way to translate photons into digital information to later be converted to video…spectacular. Of course with such wizardry, obsessive attention to detail naturally manifests. And with it, measuring contests.
When you work as an independent cinematographer, you run across a lot of “true-isms”. This particular sensor is better, that lens is sharper, this camera sucks….Facts taken as truth on their face, passed along as wisdom and rarely questioned. The unfortunate consequence of a true-ism is the persistence of misinformation amongst filmmakers. Or worse, mistakes on a project occur because of faulty knowledge. The phenomenon of true-isms hardly resides in filmmaking; to the contrary, any technical or intricate subject matter often has old wives’-tales associated with it.
Note that just like anything technical or nuanced, the exploration on this topic could fill a novel. The info here is severely truncated for brevity and clarity. We can only scratch the surface.
History of exposure size
Read up on digital cameras long enough and you’re bound to come across the topic of sensor size. Super 35, full frame, Micro 4/3….what’s the deal?
The easiest way to think of sensor size is to compare it to film. Yeah, remember that stuff? How pictures were made for a hundred years before digital? Photographic film comes in multiple formats, or size dimensions. Here’s the rub: there are dozens, maybe hundreds of film formats, often for unique or now-obsolete camera systems. The differences between formats often comes down to millimeters.
For purposes of this article, I’ll focus on two types of photographic film: 135 film, and 3-perf Super 35 film.
135 film is the technical name for Kodak’s standard 35mm horizontal film. This is the film you buy at Walgreens or Amazon.com for your SLR (yes, there was an SLR before the DSLR). Introduced in 1934, a single film cell measures 36mm wide x 24mm tall. The film advances horizontally.
Super 35 is a motion picture film standard. Introduced as early as 1956, a single 4-perf film cell measures 24.89mm x 18.66mm. But in a cinema workflow, exposing in a rectangular widescreen aspect ratio means up to 25% of the squarish film cell gets wasted. To mitigate this, some filmmakers used a 3-perforation negative pulldown process, meaning only 3 perforations of film height are exposed instead of 4. The resulting 3-perf exposure measures 24.9mm x 13.9mm.
Enter the digital sensor
It’s debatable where digital filmmaking truly took hold in the cinema industry. However, it’s generally agreed-upon that Sony was the first-to-market in the late 1980’s with their HD broadcast cameras, and certainly by 1999 in Star Wars: The Phantom Menace.
Today there are just as many digital sensor options on the market as there are film standards. In fact I’d go as far to say there’s no such thing as a standard sensor size, but merely an informal ballpark size.
If we were to discuss a detailed history of digital sensors, this article would be a book. But today I’ll focus on the three sensors “sizes” you’ll most likely encounter in the wild: Super 35, Full Frame, and Micro Four Thirds.
The “Super 35″ sensor is perhaps the most widely used in digital filmmaking if you factor in all productions, small and large. ARRI, RED Cinema, Canon, Black Magic Design…they all make a “Super 35” size sensor. And there’s a good reason why – because the dimensions mimic the 3 perf Super 35 film format.
Every lens produces an imaging circle. The size of the film gate, or digital sensor, determines the captured image. Thus, the attempt to emulate the physical size of Super 35 film.
The “Full Frame” sensor is similar, but mimics the 135 film format.
The Micro Four Thirds system is an actual standard put out by Panasonic, with an imaging area of 17.3mm x 13mm. But like the other sizes, every brand has their version of “Micro 4/3” that varies from the original. I often hear this size compared to Super 16mm motion picture film, however the Micro 4/3 really is its own beast that doesn’t have an easy comparable.
In general, the larger the sensor the better the light gathering capability, which in theory equates to a better image quality. Of course, the bigger sensors are the most expensive. And make no mistake, the Micro 4/3 is perfectly capable of cinematic use.
Crop factor? Crop sensor?
On the Internet you may run across a phrase that sounds like this: “Full Frame vs Crop Sensor cameras”. The natural implication here is that there are two classes of digital sensors: Full Frame, and everything else. Of course this is nonsense.
I’m going to go against the herd here: don’t worry about this stuff. So much nonsense gets thrown around regarding why one sensor size is better than the other, or “turning” lenses into other lenses it’ll make your head spin. The basic takeaway is this: think of your lens image as a room and the camera sensor as a peephole. The larger the peephole, the more of the image you get to see.
Of much higher importance is that you know your camera, how it behaves with different lenses, and train diligently. So unless you’re using multiple cameras with different sensors, anything to do with crop factor is pretty useless information. And if you are in charge of a multicam shoot, you probably know this stuff anyways.
But wait, there’s more
The problem with discussing digital sensor size is that, for all practical purposes, a standard Super 35 sensor doesn’t exist. Nor full-frame. Every camera manufacturer makes their sensor sizes slightly different. What it all adds up to is a ballpark slang of “Super 35” and “Full Frame” approximations. Yes, I know certain size sensors attempt to mimic specific film formats/exposures/presentations/whatever. If you know that stuff, then you know what sensor you’re choosing to use and why, which is more important than any true-ism about the sensor itself.
Also notice how I haven’t discussed anything about K’s. As in 4K, 8K ect. That’s because those numbers describe a video file resolution and really have nothing to do with the physical image sensor size. Any talk along the lines of “this is a 4k sensor” is mostly marketing speak. Find out the physical sensor dimensions and go from there.
Just to see how many “standards” there are, here are some popular sensor and film sizes compared (englarged):
Now actual size:
Just like everything else technical, debating sensor size is largely academic. None of it really matters if you can’t light a scene effectively, right? My advice is that if you’re worrying about which sensor to choose for your next project, you’re probably better off just filming with what you have. Or hire a DP that can remove the confusion for you.