photokaboom

Learn Photography

Photo Tips > Shutter Speed > Mechanical & Electronic Shutters

Mechanical Shutters

Mechanical shutters have two curtains.

The first curtain opens and light reaches the entire sensor.

Then, a second curtain closes, blocking the light.

The above sequence, in which the sensor is exposed all at once, is called a global shutter.

At shutter speeds faster than the flash sync speed (often 1/125th or 1/250th), the second curtain begins to close while the first curtain is still not fully opened.

Therefore, the sensor isn't exposed all at once.

The two curtains create a slit traveling across the sensor.

Light reaches the sensor at slightly different times.

The above sequence, in which light doesn't reach the sensor all at once, is called a rolling shutter.

Here, because the slit travels so quickly, rolling-shutter distortions are avoided.

Electronic Shutters

Electronic shutters don't have curtains.

They create the effect of curtains opening and closing by turning the camera sensor on and off.

When the sensor is turned on—each row of photosites are read out—row-by-row.

Photosites are the "cups" that gather photons on the sensor.

So, when the sensor is turned on, row 1 is recorded, row 2, row 3, etc., and then the sensor is turned off.

Cameras May Have Both

Types of Shutter

If a camera has Live View, the camera is using its electronic shutter to display the scene in the viewfinder or LCD screen.

When the shutter release is pressed, the photograph may be made using a mechanical shutter.

Some Canon cameras have a silent shooting mode called electronic first curtain.

When the shutter release is pressed, the sensor turns on and each row of the sensor is read out.

Then, the second curtain of the mechanical shutter closes.

Electronic Shutters:

Pros & Cons

Pros

• Silent

• No vibration from shutter blade movement

• Faster shutter speeds (up to 1/32,000 of a second)

However, if there's camera or subject movement, there may be distortion.

Cons

• Slow readout which distorts any subject movement

Each line of the sensor is turned on and off very quickly.

However, the lines are not readout, recorded, as quickly.

The electronic shutter may be 1/4000—but the readout may take 1/60th of a second.

If the camera or subject are moving during that 1/60th of a second—the movement will be distorted.

• No flash

• No shutter speeds below one second at low ISO values, 1/8 of a second at high ISO values

• Banding with florescent light

• Possible loss of dynamic range and increased noise at high ISO settings

Live View

If your camera has Live View, the camera is using its electronic shutter to display the scene in the viewfinder or LCD screen.

When you press the shutter release, the photograph is made using your camera's mechanical shutter.