Shutter Speed - Understanding Exposure
- Tea L
- Aug 3
- 5 min read
Updated: Sep 4
Let's cover the basics of Shutter Speed (Shutter Angle) when it comes to working with cameras. We're going to start with shorter to-the-point explanations and at the end we will dive a bit deeper, so you can use this as a quick reference if needed.
Utilitarian explanation of Shutter Speed
Shutter Speed (or shutter angle) is one of the three methods by which you control exposure, along with Aperture and ISO. Shutter Speed is measured in fractions of a second. (i.e. 1/50th of a second.) Shutter Angle is another way of describing the same process, we'll return to it in a second.
A "lower" shutter speed results in a brighter exposure (i.e. 1/50 or 180°).
A “higher” shutter speed results in a darker exposure (i.e. 1/100 or 90°).
The lower or higher distinction is based on the size of the denominator in the fraction.
The side effect of Shutter Speed is it’s effect on Motion Blur.
A "lower" shutter speed results in an increased amount of motion blur.
A “higher” shutter speed results in a decreased amount of motion blur.
Our expectation for motion blur is generally set by the standards of cinematic production, which is typically filmed at 24 fps (frames per second.) The “general rule” is that a shutter speed “twice as fast as your frame rate" results in “average” motion blur when shooting human subjects.
24fps = 1/48 or 1/50 30fps = 1/60 60fps = 1/120
This is where Shutter Angle comes in. Shutter Angle is another way of describing the same process, but uses a measure that is relative to the frame rate you are shooting and motion blur it produces.
180° Shutter Angle always produces the "standard amount of motion blur", regardless of frame rate.
Shutter angle is more likely to be found on cinema cameras (Sony FX30) as an option you can switch to in the menus, whereas it is not found on hybrid cameras (Sony A7sII / A7rIII).
If shooting cars, or other fast moving objects, a higher shutter speed may be needed.
Rendering a car with little motion blur may call for 1/100th or 1/250th shutter speed at 24fps. (or a shutter angle of 90° or 45°.)
Suggestions for using Shutter Speed when shooting
90% of the time you should just set your shutter speed to “the standard” for your frame rate and forget it.
24fps = 1/48 or 1/50 30fps = 1/60 60fps = 1/120 (Shutter Speed)
180° (Shutter Angle)
This generally gives you maximum exposure (brightness) out of the shutter speed, allowing you more freedom with Aperture while keeping your ISO low. This is because we typically worry about having too little light, rather than too much when shooting with natural light.
The exception to this rule is when shooting fast moving subjects, where you may need to use a higher setting. In that case it can be usefull to pick an acceptable higher setting and stick to that the entire time, as you would otherwise with the “standard”.
A deeper explanation of Shutter Speed
Shutter speed represents physically controlling how long each photo (or frame of video) is exposed to light.
The longer that light hits the sensor, the brighter the image will be.
A simple example to think of is what happens when you exposure skin to the light of the sun. A couple minutes may just warm you up, an hour may give you a tan, a few hours may give you a burn. The intensity may be the exact same, but the duration of that intensity has a cumulative effect. (And much like different skin tones, different sensor sensitivities will modify this relationship.)
The bi-product of this duration control is motion blur. Because the longer the light is exposed, the more chance there is of your camera moving slightly or of the subject moving slightly in the same frame, causing the image to look blurry.
This was a common issue with very early photographic technology, like the Daguerrotype, where the photosensitive plates (sensor) had such a weak sensitivity that exposure times (shutter speed) were often longer than multiple minutes. Requiring the person sitting for the portrait to remain absolutely still lest they produce motion blur.
A certain amount of motion blur is often expected in film and video, though this variable also depends on the speed of the object you are seeking to capture.
I.e. a bullet train is much faster than a car on a residential street is much faster than a person walking. Therefore each requires a different setting to render the motion “crisply”.
Mechanically, in a classic film camera or DSLR, the camera’s default state is to have the shutter closed, blocking any light from reaching the film, thus keeping you from wasting a frame by overexposing it.
This also provided you the ability to see through the lens of the camera (depending on the design) as a mirror would drop down in front of the shutter to bounce the light away from the film plane (or sensor) and up into the eyepiece, allowing you to see.
When you would press the shutter, the mirror would retract (you would lose the ability to see through the eyepiece), the shutter would open as determined by your shutter speed, the shutter would close, the mirror would drop back down and the film would progress through the camera then providing a new frame to expose. (Or the camera would save the data to a memory card.)
This is slightly different on modern mirrorless cameras, so named because they omit the mirror and instead display a read-out of the sensor to a rear screen or digital viewfinder.
In these cameras, the photo mode usually uses the physical shutter (largely as described above) and the video mode simply “cuts” the readout at a specific time interval to simulate the physical shutter.
The Pro of this approach is the lack of a loud “ticking” sound at each actuation of the shutter, multiple times a second. Which historically made shooting in small spaces with sync sound very difficult.
The Con is the introduction of Rolling Shutter a phenomenon where larger and faster movements cause straight lines to look bent. (I.e. a whip pan with a bad rolling shutter will make a light post look curved during the pan.)
This depends on how quickly the camera’s processor and read data from it’s sensor. If there is a slight delay between when the top most pixels are read and when the bottom most pixel is read, it causes this “bending”.
Rolling shutter depends on the specific camera and sensor being used, with high end RED or ARRI cinema cameras having a Global Shutter, which means the processor reads each pixels of each frame at exactly the same moment, eliminating the rolling shutter issue without the need for a physical shutter to cut the light.
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