Understanding Shutter Speed : Effects on Exposure and Motion

 

vyas-river

Vyas (Bias) river at Manali

To understand the exposure, it is essential to learn the exposure triangle I’ve introduced in earlier post. Let us move towards the factor which effects exposure as well as visual motion, Shutter speed.

What is Shutter Speed?

Shutter speed is the amount of time for which photographic film or sensor is exposed to light. When shutter release button is clicked, camera shutter opens and allows the light to fall on camera sensor. Shutter is open for time according to the value we select, so longer the shutter is open, more is the amount of light we get on sensor. So if shutter is open for longer time, image will be brighter, and for shorter time image will be darker.

Value in blue box indicates the shutter speed

Value in blue box indicates the shutter speed

Shutter speed is measured in seconds, generally in fractions of second. you must have seen values like 1/125, 1/1000, 2″ on display scree. Those values indicate the shutter speed. For example, value 1/100 indicates that shutter will be open for 1/100th fraction of second, 1/60 indicates 60th fraction of second. DSLR also provides long exposure time.

value 2″ indicates that shutter will be open for 2 seconds. In addition some SLRs provide “BULB” mode in which we can keep shutter open as long as we want.

Shutter speeds available to you on your camera will usually  approximately double with each setting. As you move your main dial to change the value, it will change in order of 1/60, 1/125, 1/250, 1/1000 and so on, (or opposite order). Nowadays DSLRs also provide intermediate values. Proper shutter speed is selected to get a perfect exposure

Relation of motion and shutter speed

Relation of motion and shutter speed

Controlling Motion

Basically Shutter speed is related to motion in image. We select its value according to the scene in frame. For example, in sports games, we would like to freeze the motion in frame. But in night photography, like a streets at night, trails of vehicle lights create a beautiful frame, thus continuous motion or motion blur can also be artistically wonderful.

So few questions always arise in our mind, What is the correct shutter speed that we should select? what are the equipments we should use and precautions to take?

When considering what shutter speed to use in an image you should always ask yourself whether anything in your scene is moving and how you’d like to capture that movement. When you want to freeze the motion, faster shutter speed value is chosen (in reference of saying faster, 1/1000 is faster than 1/500).

But as you increase this value in denominator (1/value), your image will get darker and darker, so to get the perfect exposure, either you decrease this value as much as you can, or change other effecting factors, aperture and ISO values. As you goes on decreasing the shutter speed, i.e. increasing the shutter open time, more will be the motion captured. It can be illustrated by following image.

Effect of shutter speed

Effect of shutter speed

Now there are few things that we should take care care of while taking images on slower shutter speed. while taking images in motion or at night time, at slower shutter speed, camera shake effects your image. Camera shake is movement of camera while shutter is open which results in blurred images. Generally we are responsible this camera shake as it is quite difficult to hold the camera so steady for longer time. Nowadays lenses are designed with “image stabilizer” function to eliminate this movements, but this function is good only up to shutter speed of 1/20 or 1/10 seconds.

So if you are using much slower shutter speed, then you’ll definitely need some support to keep your camera steady. And here we use tripods! While taking images on shutter speed like 2 seconds, 10 seconds, it is recommended that you should use the tripod to get steady and sharp images with the creativity you have filled in it! And yes, if you are using slower shutter speed, more amount of light will be there and image could get much brighter. So to get correct exposure, set other two values accordingly.

Focal length and Shutter Speed

There is one more thing that we must take care of. Focal length also effects the shutter speed. If you are using smaller focal length to capture in wide angle, the it is possible to keep slower shutter speed. But at larger focal length, shutter speed should be little faster. It is because, at larger focal length, you are focusing on very distant object. So small camera shake can effect greatly at this frame, which we could have neglected for wide angle frame.

So while winding up this topic, I’d like to say that what shutter speed value to choose always depends on your creativity. Freezing the movement is fun. But motion blur is also a wonderful factor to create a masterpiece. More you experiment with the shutter speed, more wonderful results you’ll get and more you’ll learn about the exposure. Here are few images I’ve captured at different shutter speed values. I hope you folks will like them!

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