These days, it seems everyone is jumping on the “bigger is better” bandwagon when it comes to image sensors for motion picture use. But is a large format sensor better for your project? Well, that honestly depends on your project.
What Are Your Sensor Size Options?
Arri recently announced their Alexa Min LF. This camera has a 36.70 x 25.54 mm sensor. Canon has released a number of 4k cameras with the “full frame” sensor that is 36 x 24 mm. (as I am writing this, Canon finally announced an “APS-C” 22 x 15mm sensor size model camera that shoots 4k: the Rebel SL3.) The Red Monstro 8k has a sensor size of 40.96 x 21.60 mm, the Red Helium 8k uses a 29.9 x 15.77 mm sensor the Gemini 5k uses a 30.72 x 18 mm sensor and the Dragon-X uses a 25.6 x 13.5 mm sensor. Then there are micro 4/3 camera like the Black Magic Pocket Cinema 4k and the Panasonic GH5 that use a 17.3 x 13 mm sensor. (As a point of interest, the iPhone XS Max has a Sensor size of 7.01 x 5.79 mm and the GoPro Hero 7 Black has a sensor size of 6.17 x 4.63 mm)
How Do These Compare To Film?
When talking about film, it is incorrect to do a pixel to grain comparison. However, frame size is important. The film gate compared to the sensor size is important, and we will go into detail as to why later. As for what the frame sizes actually are when talking about film?
Super 16mm has a frame size of 12.52 x 7.41 mm. Super 35mm uses a frame size of 24.89 x 18.66. Standard Academy 35mm has a frame size of 21.95 x 16mm. Vista Vision used a frame size of 37.72 x 24.92 mm. And last, but not least, is 70mm Imax that uses a frame size of 70.41 x 52.62 mm.
So, as you can clearly see, even though Micro 4/3 is commonly referred to as “16mm equivalent” at 17.3 x 13 mm it is actually a bit larger then real Super 16mm at 12.52 x 7.41 mm. Likewise, APS-C sensors at 22 x 15 mm are very close to Academy Standard at 22 x 16 mm. When you start getting to the Large Format sensors like Arri and Red are using, you end up being closer to Vista Vision size.
The image on the right shows a Micro 4/3 sensor next to a 16mm film gate. You can clearly see that the Micro 4/3 sensor size is dramatically larger then the 16mm film gate size. Some companies like Black Magic like to advertise Micro 4/3 as a Super 16mm size sensor, and we can clearly see that it is actually bigger. Granted, this image is of standard 16mm, but the difference is in width (Super 16mm eliminates one set of sprockets in the film allowing you to shoot with a wider frame. Super 16mm is 12.5 x 7 mm while standard 16mm is 11.5 x 7mm)
How Does Frame / Sensor Size Affect My Image?
Studies have shown that the human eye can’t tell the difference between images above 3k resolution. (here is a great article to delve deeper into that subject). Back in the days of film, a larger negative meant better image quality. But today, a 4k image shot on a micro 4/3 sensor has the same image quality as a 4k image shot on a large format sensor. This doesn’t mean that shooting 6K or 8K isn’t good. If you are shooting a lot of FX shots, or need to re compose shots in post, then these are necessary tools. But for most of us, 4K is good enough.
Where frame / sensor size really comes into play is Depth of Field.
Simply put, the larger your sensor, the narrower your Depth of Field. Most people will agree that a narrow depth of Field is more cinematic. It gives us the opportunity to put just what we want the audience to pay attention to in focus.
However, frame / sensor size isn’t the only factor that can change the Depth of Field. Both Focal Length and Aperture size also have an affect on Depth of Field. The longer the focal length, and the wider the Aperture, the narrower the Depth of Field.
If you are a production with a large budget, shooting on stage, with ample lighting and crew, then large format can work great for you. You can light your scene well enough that you can shoot at f/5.6 (because most lenses are better in the middle of the aperture settings), you can do a lot of rehearsals to make sure everyone is getting to their marks at the right pacing, and you are using top quality cast and crew that can hit their marks, and nail the dolly move, and get perfect focus racks. Therefore, the narrower Depth of Field on a large format camera isn’t an issue.
When is Smaller Better?
However, if you are shooting a low budget production, you are probably on location and shooting wide open because you are lighting with house power and a budget friendly lighting package. You don’t have the time for hours of rehearsals, and numerous takes. Your cast doesn’t have the years of experience necessary to hit their marks perfect every time, your AC and /or/ your Dolly Grip may be a little green, or you have a not top of the line dolly than Depth of Field can cause problems.
In cases like these, you would save yourself a lot of time and takes to have a smaller sensor. I prefer APS-C because you will still get basically the same look as a film shot on Academy Standard, and your lenses will work the way you would expect them to if you had a Panavision 35mm camera. I also believe Micro 4/3 is adequate in these situations. There are many great films shot on Super 16mm, and your frame / sensor size will be larger than that.
If you are shooting “gorilla” style, a lot of run and gun style, or found footage style, then Micro 4/3 may be the biggest sensor size you want to use. In those situations, you don’t want to loose a shot because it was a little soft.
Recently, a friend of mine was telling me that the shows that she works on are always having trouble finding and keeping AC’s. As we talked more, I realized that these shows all had lower budgets that caused the shows to hire less experienced cast and crew (some of these are nationally syndicated TV shows…) However, the all had to have the biggest and best camera. I explained to her that when you have a less experienced cast and crew, inadequate lighting and a large format sensor on your camera, you are setting up your AC for failure. If your Depth of Field becomes so narrow that you can have someones eyes in focus and the tip of their nose is soft, your Talent, your Dolly Grip and your AC all have to be at the top of their game to get the shot in less than a dozen takes.
So is a large format sensor always better? No. You need to choose the sensor size that best fits your production. Or, in some cases, that best fits the look your cinematographer wants to achieve.
Smaller Can Be Better
Many of you readers are familiar with the film “American Psycho”. If you look at Andrzej Sekula’s cinematography in that film, you will notice they have a very long Depth of Field. Much of the movie feels hyper realistic because of the perceived sharpness of everything around.
To obtain that long Depth of Field, the films crew pumped so much light onto set that the set was always uncomfortably hot.
If you tried to recreate that look for a project today, you could save yourself a at least a couple stops by using a micro 4/3 sensor over a large format sensor. That means you could get the exact same look with less lights being used, and shorter turn around times between shots as well as a more comfortable shooting environment.
If you were daring, you could even shoot on an iPhone.
One of the best sound guys I know, Steve Hitselberger is putting together a reality show about beer (and the people who drink it), and asked me to cut together a sequence for him.
He shot the sequence on his iPhone. Not only did the iPhone allow the shooting to be unobtrusive and result in more natural interactions, It also had a very long Depth of Field that nearly eliminated the threat of loosing a shot over focus issues.
What To Remember About Frame / Sensor Size
As technology advances, pixel counts will continue to go up and costs will go down. At this years NAB (2019), Sharp announced an 8k Micro 4/3 camera that they plan to sell for between $3,000 and $5,000. However, I don’t see much sense in sensor sizes going much larger the Imax size. (although I would like to see a 4 x 5 or 8 x 10 image sensor…) For cinema, I believe that sticking with the old film sizes work best because we already have so much compatible glass… Anyway, having too narrow of Depth of Field may be great for certain looks, an advertisement, or a music video, however, it isn’t something that would work well across most feature films.
Instead of making larger sensors, we should be working on things like: better latitude. Higher sensitivity. Better quality image compression. Let’s figure out how to deliver near loss less image quality to someone sitting in a tent in the forest and stop using larger image sensors that don’t do anything good for anyone.