The shutter controls the exposure time, i.e., how long light hits the sensor. There are three types: leaf shutter (simultaneous exposure, ideal for flash), focal-plane shutter (metal curtains, short times, but possible image distortion), and electronic shutter (silent, very short times, rolling shutter effect possible). Flash sync speed is especially important for focal-plane shutters.
Category: Photography Basics > 2. Camera Technology & Construction Article ID: 2.8 Created: May 2026
Key Points in Brief
- The shutter controls how long light falls on the sensor (or film) – it determines the exposure time
- There are three types: leaf shutter, focal-plane shutter, and electronic shutter
- For the focal-plane shutter, the flash sync speed must be observed – the shortest time at which the entire sensor is exposed simultaneously
Explanation
What Does the Shutter Do?
Sensors and film are extremely light-sensitive. Without a shutter, even normal daylight would cause complete overexposure within milliseconds. Therefore, the shutter is normally closed – it only opens during the set exposure time (e.g., 1/500 s) when the shutter release is pressed, then closes again.
Typical exposure times in a stepped sequence (each step halves the amount of light):
8 s → 4 s → 2 s → 1 s → 1/2 s → 1/4 s → 1/8 s → 1/15 s → 1/30 s → 1/60 s → 1/125 s → 1/250 s → 1/500 s → 1/1000 s
The Three Types of Shutters
1. Leaf Shutter
- Consists of curved blades that open and close from the center outward
- Exposes the entire sensor simultaneously – ideal for flash photography (no flash sync speed limitation)
- Common in: compact cameras and large format cameras
- Disadvantage: Very short exposure times (under 1/1000 s) are difficult to achieve
2. Focal-Plane Shutter
- Consists of two metal curtain systems (curtain 1 and curtain 2)
- Operating principle: curtain 1 opens → sensor is exposed → curtain 2 closes
- At very short exposure times, curtain 2 closes before curtain 1 is fully open → a moving slit forms that exposes the sensor progressively
- Allows extremely short times up to 1/4000 s or more
- Common in: DSLRs and mirrorless cameras (DSLMs)
- Disadvantage: For fast-moving subjects, the slit can cause image distortions (e.g., helicopter rotors or race cars)
Flash Sync Speed with Focal-Plane Shutter: Because the entire sensor is only simultaneously open below a certain exposure time, there is a flash sync speed (typically 1/125 s to 1/300 s). At shorter times, curtain 2 already covers parts of the sensor – the flash would then only illuminate a strip.
3. Electronic Shutter
- No mechanical parts – the sensor is switched on and off purely electronically
- Enables very short times (up to 1/16,000 s) and is silent
- Common in: mirrorless system cameras (DSLM) in silent mode
- Disadvantage: Can also cause distortions with fast movements (rolling shutter effect), since the sensor is read out line by line – not all pixels simultaneously
Shutter Types Compared
| Feature | Leaf Shutter | Focal-Plane Shutter | Electronic Shutter |
|---|---|---|---|
| Flash Sync Speed | No limitation | 1/125–1/300 s | No limitation |
| Shortest Exposure Time | ~1/1000 s | ~1/4000–1/8000 s | ~1/16,000 s |
| Noise | Quiet | Clearly audible | Silent |
| Distortion with Movement | No | Possible | Possible (Rolling Shutter) |
| Typical Camera | Compact, Large Format | DSLR, DSLM | DSLM (Silent Mode) |
Practical Tip
Anyone who regularly photographs with flash should know their camera’s flash sync speed and never go below it – otherwise, only part of the image will appear exposed. For most DSLRs, it is between 1/125 s and 1/200 s. It is listed in the camera’s technical specifications.