Because light levels change, digital cameras must vary the amount of light reaching the sensor. A shutter is a mechanical device that opens and closes quickly, altering the length of time that the sensor is exposed to the light.
This is the amount of time that the camera’s shutter remains open. The longer the shutter is open, the more light can enter and fall on the sensor. If the shutter is open too long, the image will be overexposed (there will be too much light entering and hitting the sensor) or in other words burned out. Overexposure means the highlights are washed out, there is no detail in them, only white pixels. But if the shutter isn’t open long enough, the exact opposite happens: there won’t be enough light for the sensor to register, so the image will be too dark (underexposed).
Most DSLRs use a Focal Plane Shutter. It is positioned immediately in front of the focal plane of the camera (right in front of the sensor), and uses two shutter curtains.
Fig. 1 - the sensor is covered by the 1st curtain (red rectangle).
Fig. 2 - the 1st curtain moves away, and the sensor is now exposed to light.
Fig. 3 - after the exposure, the 2nd curtain covers the sensor, finishing the exposure (green rectangle).
When you have a fast shutter speed, the representation changes a bit.
Fig. 2 - the 1st curtain moves away, and the sensor is now exposed to light.
Fig. 3 - after the exposure, the 2nd curtain covers the sensor, finishing the exposure (green rectangle).
When you have a fast shutter speed, the representation changes a bit.
Fig. 1 - the sensor is covered by the 1st curtain.
Fig. 2 - the 1st curtain starts to move to the left and allows the exposure to be made. But because this exposure requires a very fast shutter speed, the 2nd curtain starts to move in, at a set distance from the first one
Fig. 3 - the 1st curtain continues to travel across the sensor followed by the 2nd curtain.
Fig. 4 - the 1st curtain finishes moving, followed closely by the 2nd curtain which is now covering the sensor completely, finishing the exposure.
It would be pointless to use a flash with this shutter speed, as the short duration of the flash would only expose a very small amount of the frame, as the rest is covered by either the first or second curtain. So when using flash, the max shutter speed is 1/200 or 1/250sec (depending on camera model). This is called the X-sync speed, but I will explain that in another article.
Fig. 2 - the 1st curtain starts to move to the left and allows the exposure to be made. But because this exposure requires a very fast shutter speed, the 2nd curtain starts to move in, at a set distance from the first one
Fig. 3 - the 1st curtain continues to travel across the sensor followed by the 2nd curtain.
Fig. 4 - the 1st curtain finishes moving, followed closely by the 2nd curtain which is now covering the sensor completely, finishing the exposure.
It would be pointless to use a flash with this shutter speed, as the short duration of the flash would only expose a very small amount of the frame, as the rest is covered by either the first or second curtain. So when using flash, the max shutter speed is 1/200 or 1/250sec (depending on camera model). This is called the X-sync speed, but I will explain that in another article.
Shutter speeds are the denominators of fractions. The larger the 2nd number, the less light reaches the sensor. They usually start at 30sec, and go up to 1/4000 or even 1/8000 in high end DSLRs. You also have the B - bulb mode, where the shutter simply stays open as long as the shutter release button remains pressed.
Example: let's say a basic exposure is 1/250 of a second at f/16. If you wanted to stop fast-moving action, you might want your camera to switch to 1/500 of a second to freeze the movement. Because you’ve cut the amount of light in half by reducing the shutter speed from 1/250 to 1/500, your camera needs to compensate by doubling the amount of light admitted through the lens. That means opening up the aperture from f/16 to f/11 to let in twice as much light.
So an exposure of 1/250 second at f/16 is equivalent to an exposure of 1/500 second at f/11.
Using the bucket in the rain example, if you leave the bucket 2 seconds in the rain, you will collect X amount of water in it. Leave it 1 second, and you only get half of X. Pretty logical, right? So how do you collect the same amount of water but in a shorter time?
Example: let's say a basic exposure is 1/250 of a second at f/16. If you wanted to stop fast-moving action, you might want your camera to switch to 1/500 of a second to freeze the movement. Because you’ve cut the amount of light in half by reducing the shutter speed from 1/250 to 1/500, your camera needs to compensate by doubling the amount of light admitted through the lens. That means opening up the aperture from f/16 to f/11 to let in twice as much light.
So an exposure of 1/250 second at f/16 is equivalent to an exposure of 1/500 second at f/11.
Using the bucket in the rain example, if you leave the bucket 2 seconds in the rain, you will collect X amount of water in it. Leave it 1 second, and you only get half of X. Pretty logical, right? So how do you collect the same amount of water but in a shorter time?
By getting a 2x wider bucket (opening up the aperture). That way in 1 second you will be able to collect the same amount of water as with a normal bucket in 2 seconds.
Shutter speed and exposure time refer to the same concept. A faster shutter speed means a shorter exposure time.
With waterfalls and other creative shots, motion blur is sometimes desirable.
Shutter speed and exposure time refer to the same concept. A faster shutter speed means a shorter exposure time.
|
Shutter Speed
|
Examples
|
|
1 - 30+ seconds
|
Specialty night and low-light photos on a tripod
|
|
2 - 1/2 second
|
To add a silky look to flowing water
|
|
1/2 to 1/30 second
|
To add motion blur to the background of a moving subject
Carefully taken hand-held photos with stabilization |
|
1/50 - 1/100 second
|
Typical hand-held photos without substantial zoom
|
|
1/250 - 1/500 second
|
To freeze everyday sports/action subject movement
Hand-held photos with a telephoto lens |
|
1/1000 - 1/4000 second
|
To freeze extremely fast, up-close subject motion
|
With waterfalls and other creative shots, motion blur is sometimes desirable.
Now you may ask how do you know which shutter speed will provide a sharp hand-held shot? The answer is simple: experiment. Take some pictures, and view them on the camera's LCD screen at 100% zoom. If a properly focused photo comes out blurred, then you'll usually need to either increase the shutter speed, keep your hands steadier or use tripod.
One way to find out how low can you go hand-held is to take a photo of a street at night (one that has street lights). If the lights look round when you zoom in to 100%, that means you have no motion blur and you can go lower with the shutter speed. However if they look oval or come out as lines, that means you have motion blur. So you need to up the shutter speed (or open up the aperture, or increase the ISO).
Some people say that your minimum shutter speed should be 1/focal length. In other words 1/ the “length” of your lens. Say you have a 50mm lens, so your minimum shutter speed should be 1/50 second. Using a 300mm telephoto lens, your minimum shutter speed should be 1/300s to get a photo with no motion blur.
This is partially true. Partially, because if you have a 300mm lens with good Image Stabilization, then you can go lower than 1/300 second.
Some people say that your minimum shutter speed should be 1/focal length. In other words 1/ the “length” of your lens. Say you have a 50mm lens, so your minimum shutter speed should be 1/50 second. Using a 300mm telephoto lens, your minimum shutter speed should be 1/300s to get a photo with no motion blur.
This is partially true. Partially, because if you have a 300mm lens with good Image Stabilization, then you can go lower than 1/300 second.
