Shutter Angle In Cinematography Explained
INTRODUCTION
One of the key things that makes cinematography different from photography, painting or illustration is, of course, that cinematographic images create an illusion of movement.
How smooth, or jerky this motion appears when captured is dependent on the important camera setting of shutter angle or shutter speed. Let’s use this video to unpack what shutter angle is, explain the differences between shutter angle and shutter speed and then look at some examples from movies that have used the shutter to create interesting visual effects.
WHAT IS SHUTTER ANGLE?
A useful exercise is to think of a filmed clip not as one glob of video, but rather as a series of individual photographs, or frames, that are played back fast enough to create an illusion of motion.
Shutter angle controls how much motion blur there is in a single frame. An angle of 360 degrees will create more of a streaky blur when a character moves, while an angle of 45 degrees will create a sharper, crisper, stuttering image. But what exactly is a shutter angle and how do we arrive at those numbers?
Inside old film cameras, an image is created when light passes through a lens and hits a frame of film. In between the lens and the film there is a rotating circular disk which is called a shutter that determines how much light is let through.
Usually these old film camera shutters could be mechanically opened up to different angles from around 11 degrees to a maximum of 180 degrees. Modern digital cinema cameras however are capable of digitally dialling in specific shutter angles all the way up to 360 degrees.
The amount that this circular shutter is solid and blocks light versus open and lets light in is called the shutter angle.
For example, if the shutter is set to 45 degrees it means that it is open for 45 degrees of the 360 degree circle and closed for 315 degrees. Light will hit and expose each piece of film only when it passes through the small open portion of the 45 degree shutter. This small exposure time means that a miniscule moment is frozen in every frame, which means the image will have less motion blur. Therefore, when multiple frames captured with a 45 degree shutter that all look sharp and crisp are played back it gives a stuttering effect and renders small moving details sharply.
For an opposing, theoretical example let’s imagine we could open the shutter up all the way to 360 degrees. This would mean each frame is exposed for much longer and therefore this shutter angle would let through more light. Because the exposure time is much longer, there is a greater period to capture movement, which means each frame will have more motion blur. Therefore when multiple frames captured with a 360 degree shutter are played back it gives a burred, lagging feeling to movement and renders small moving details with a hazy smoothness.
Both of these shutter angles are generally considered to give an exaggerated appearance of motion that is unnatural - one that is overly choppy and one that is overly blurry.
The middleground is a 180 degree shutter. This is widely considered to be the default shutter angle setting on a camera as it produces motion which looks most natural to the human eye. The vast majority of movies that you watch will use a 180 degree shutter for most scenes.
Many digital video cameras come with the ability to adjust their shutter, however this isn’t done by changing a physical mechanical shutter like on older film cameras. This adjustment is instead done by changing the amount of time that the digital sensor collects light for each frame which is captured.
So to sum this up, a smaller shutter angle means less light will hit the film plane, and that images will be sharper and appear more choppy and stuttering when played back. While a larger shutter angle means more light will be let through, images will be more blurred and will have a smoother motion when played back.
SHUTTER SPEED VS SHUTTER ANGLE
If you use a broadcast or consumer video camera rather than a cinema camera, the measurement of the shutter will likely be displayed as a shutter speed rather than a shutter angle. Shutter speed is rooted in the same fundamental concepts as shutter angle but with a few small differences.
Instead of being displayed as the angle of the shutter that blocks the light, it is displayed as the amount of time that each individual frame is exposed to light for.
A good rule of thumb to get to an equivalent 180 degree shutter angle is to take the frame rate that you are shooting at, for example 25 frames per second, and double it - so a shutter speed of 1/50th of a second.
This is the reason that tutorial videos talking about camera settings will advise you to use a 50th of a second shutter speed on DSLR or mirrorless cameras.
The issue with using shutter speed, and why it isn’t used on high end cinema cameras, is because it requires you to do slightly clunky calculations about shutter speed every time you want to change the frame rate on the camera.
Many cinematographers want to maintain the same feeling of normal motion blur by using a 180 degree shutter angle across the whole project. On cinema cameras you can set it to 180 degrees and leave it there, so that whether you are shooting at 24, 33, or 200 frames per second, you will always have the same shutter angle that produces the same feeling of motion blur. However if you’re using shutter speed and you want to maintain the same 180 degree shutter angle then you need to perform a calculation and change the shutter speed setting every time that you want to shoot at a different frame rate.
If you’re shooting at 24 frames per second and want a 180 degree shutter angle, the shutter speed must be doubled, or set to 1/48. If you change to shoot 60 frames per second then you need to change the shutter speed to 1/120. At 200 frames per second your shutter needs to be 1/400th of a second.
Using shutter angle eliminates the need to change the shutter speed when you alter the frame rate on the camera. It does it automatically so to speak.
Another reason that cinematographers may want to use angle rather than speed is that it gives you the ability to dial in a very specific shutter. For example, sometimes DPs shooting at 24 frames per second like to shoot with a shutter angle of 172.8 degrees. This is because when shooting in countries that use 50HZ electricity to power lights, they will not have an undesirable flickering or strobing effect when the camera shoots at 172.8 degrees.
CREATIVE USES
Let’s take a look at some different examples of how shutter angle can be used to subtly further storytelling in movies.
The first shows how a narrow shutter angle can be used to introduce a jittery feeling of urgency and panic that recreates the emotional reality of on the ground warfare.
“Saving Private Ryan was never meant to be thrilling. It was never meant to be an adventure. It was meant to be a recreation, a kind of a documentation, of the closest I could get to the experiences of those who fought there. All the research that we did really brought that scene to life because it was ugly. Because it was honest. And it had to be ugly because that’s the way it was.” - Steven Spielberg, Director
Cinematographer Janusz Kamiński decided to shoot most of the famous opening scene in Saving Private Ryan using either a 45 degree or a 90 degree shutter. This, along with the use of a handheld camera gave the footage a crisper shake and imparted an added sense of reality and urgency to the scene.
Using a narrow shutter angle also had a pronounced effect on the explosions that were happening around the characters. If we pause on a frame with an explosion you can see individual chunks of sand flying through the air. Because of the shorter exposure time there is less motion blur so every individual grain of sand stands out as crisp - giving the scene a literal grittiness.
Digital cinema cameras came onto the scene with an added ability that film cameras didn’t have. Being able to shoot with a wide shutter angle past 180 degrees. One of the earliest examples of a filmmaker using this technology reportedly occurred in the shooting of Michael Mann’s Collateral.
Shooting with a wide open shutter angle served two purposes. First and foremost it let more light into the camera. This allowed them to shoot night exterior shots in very low light conditions - which they otherwise wouldn’t have had enough light for.
Visually it also gave the city a more blurry, hazy, glowing feel which made the city itself almost feel like one of the movie’s characters. It’s an interesting example of letting the camera shape the feeling of the environment on screen.
“It was night time and I just cranked the shutter open and went down to 6 frames. If you can’t afford to do something it’s good to find a solution that gives the feeling of something. You have the impression of a battle and a fight rather than saying, ‘Oh, he was there and he went that way and the horse went this way.’ It was the feeling of it. It was the emotion of being in a battle rather than the historical outlay of who and where and when they crossed the line.” - John Mathieson, Cinematographer
John Mathieson pulled from two different techniques - shutter speed and frame rate - when shooting the battle scenes in Gladiator to effect the feeling of motion in the image. On the one hand, he used a choppy 45 degree shutter angle to reveal the sword’s movement as it swung around wildly, which increased the feeling of intensity and made the combat feel more aggressive and sharper.
On the other hand he employed a different technique, separate from shutter angle, to increase motion blur and slow time down. He did this by shooting with a slow frame rate of 6FPS that allowed the film to be exposed for much longer and therefore blurred any movement. These 6 frames were then printed four times using step printing to arrive at a frame rate of 24 frames.
Combining these two different approaches to movement meant that action scenes were shot in a more experimental way that emphasised the emotions and feeling of being in a battle rather than just trying to portray it accurately.