Let us now dive deep into understanding another most important aspect of Photographic Exposure, Shutter Speed.
Shutter speed indicates the duration of time the shutter is open to allow light to fall onto the Camera sensor.
While Aperture dictates the amount of light that falls onto the sensor, Shutter speed dictates the duration.
Shutter speed is depicted in seconds or fraction of a second. There are standard values defined for the Shutter speed like:
30 sec, 15, 8, 4, 2, 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, 1/8000
These Shutter speed values work very similar to that of standard Aperture values. Each Shutter speed value allows the light for a duration that is:
- double the next Shutter speed value, and
- half the previous Shutter speed value
For example, Shutter speed value of 1/15th of a second, allows the light for a duration that is:
- double that of 1/30th of a second, and
- half that of 1/8th of a second
This doubling and halving mechanism of Shutter speed and Aperture values help you in achieving the desired exposure based on artistic needs.
For instance, you may need to achieve a Shallow DOF (Depth of Field) while photographing your beloved ones. Consider that the Camera meter indicates that you should be using an Aperture of f/11 and Shutter speed of 1/250th of a second.
You could set the aperture value to f/4 (to achieve Shallow DOF) and increase the Shutter speed (which means decrease the duration of the shutter) to 1/2000th of a second to achieve the same Exposure.
Below table gives you an idea:
Needed Exposure to expose our example scene properly
Results in same exposure as above
Results in same exposure as above
Results in same exposure as above
All 4 combinations result in the same Exposure for the example scene that we considered. Based on your need, you could either change the Aperture value or the Shutter speed value or both to achieve the required exposure.
Usually you decide on the Shutter speed based on three major needs:
- To Avoid Camera Shake
- To Freeze the Action
- To Achieve Motion Blur
How to Avoid Camera Shake
General rule of thumb to avoid any Camera shake is to choose a Shutter speed that satisfies the following condition:
Min. Shutter Speed to Avoid Camera Shake = 1 / Effective Focal Length
Effective Focal Length is calculated based on the Sensor size.
- For a Full-Frame Sensor, effective focal length is same as the focal length since there is no cropping.
Effective Focal Length = Focal Length of the Lens
- For a Cropped sensor, effective focal length is crop factor times the focal length.
Effective Focal Length = Crop factor of the Sensor * Focal Length of the Lens
For example, if you are using a 400mm lens on a Full-Frame Sensor (like Nikon D4 or Canon 1DX), you need a Shutter speed of atleast 1/500 (closest Shutter speed value of 1/400) to avoid any possible Camera shake.
If you are using a 400mm lens on a Cropped sensor, say 1.5X size, then you need a Shutter speed of atleast 1/1000 (closest Shutter speed value of 1/(400*1.5)) to avoid any possible Camera shake.
However, Image Stabilization (IS)/ Vibration Reduction (VR) technology can help to reduce these numbers considerably.
If you have IS/VR that gives 2-stops stabilization, then for the same focal length, you could choose a Shutter speed that is 2-stops lower than 1 / Effective Focal Length.
For example, for a Full-Frame Sensor with 400mm lens, you could go with Shutter speed of 1/125 instead of 1/500.
Another option is to use the Tripod. Tripod is very useful in Landscape photography where we need long exposures.
However, for action photography it may be limiting to use the Tripod. Though, it is possible to use Gitzo tripods with Wimberly heads, it may turn out to be expensive.
How to Freeze the Action
One of the most important aspects of Wildlife/Bird/Sports Photography is to freeze the action. Freezing the action depends on the speed at which the action happens. There is no ideal Shutter speed that suits for all purpose.
In general, the Shutter speed should be faster than the actual speed of the subject in order to freeze the action.
Shutter speeds of 1/1000, 1/2000, and so on usually helps to freeze the fast moving actions. However, this may lead to underexposure since we are allowing lesser and lesser light to fall onto the Sensor.
Since we know that Shutter speed and Aperture go hand-in-hand we can choose larger Aperture sizes (allowing more light) and shooting in day light, so that we can use higher Shutter speeds without underexposing the scene.
If the subject is moving slowly, then slower Shutter speeds like 1/125, 1/250, 1/500 may be sufficient to freeze the action. However, as you are aware, you need Shutter speed of (1/effective focal length) to minimize the Camera shake.
In such cases, you can either consider using higher Shutter speeds or make use of VR/IS system to compensate for the Camera shake.Download Beginner’s Guide to Photography to learn simple techniques.
How to Create Motion Blur
Motion blur indicates the movement in time in an otherwise frozen frame. Motion blur can be used either to show the motion or to create some artistic results.
In general, the Shutter speed should be slower than the actual speed of the subject in order to create motion blur.
Shutter speeds between 1/15 sec and 30 seconds usually helps to blur the moving action to produce motion blur. However, choosing very slow shutter speed results in too much of light falling onto the Sensor. This could be compensated either by using smaller Aperture values (f/11 to f/32) or by using Neutral Density (ND) filters.
Motion blur technique is most widely used in Landscape photography especially in the Seascapes, Cloudscapes and Waterfalls. In these scenarios, blurring the motion of the flowing water or the moving clouds could yield to very artistic results.
While going for Shutter speeds less than a second, one should go for very sturdy tripod to avoid any Camera shake.
Motion blur is also used in Wildlife/Bird Photography to show the motion in a chase sequence, birds in flight, etc. If done properly, motion blur photographs of wildlife could yield excellent results.
To create motion blur in Wildlife/Bird Photography, one has to considering using the Shutter speeds that are little less than the actual speed at which the bird is flying or the animal is running/chasing.
It takes number of iterations and experience to pull out a very good motion blur photograph of an Animal or a Bird. But it is a challenge that every Photographer should look forward to.
Only the legs of a running animal or the wings of the bird should be blurred keeping the rest of the body in focus to get excellent results. However, it is possible to show a flock of birds with Motion blur technique to create some artistic results.
Motion blur technique is also widely used in night photography to create light painting with city lights, street lights, moving vehicles, stars, etc.
How to Create Motion Blur using Panning
Generally, motion blur is created by blurring the subject showing the motion. There is another interesting way to create Motion blur; by panning the Camera!
In this case, we pan the Camera to track the moving subject. This way we can freeze the action but let the background go blur due to Camera panning.
This technique needs lot of skill as you have to pan the Camera almost at the same rate as the speed of the subject to freeze the action.
Camera Shake Vs Motion Blur
Note that Camera shake is not same as Motion Blur. Motion blur happens due to movement by the subject that we are photographing while Camera shake is due to the movement by the Photographer while tripping the Shutter button.
A Small Exercise to understand Shutter Speed
It is very easy to understand the effects of Shutter speed at your home! Just follow these steps.
- Consider a moving subject that rotates on its axis like Fan, Bicycle wheel, Skate wheel, etc
- Let the subject run at some predefined speed
- Place the Camera on Tripod
- Choose Shutter Priority Mode on your Camera mode dial. Shutter Priority allows you to select the required Shutter speed and the rest will be taken care by Camera
- Start taking photographs with various Shutter speeds ranging from 1 sec to 1/4000th of a second
Take a look at all the photographs that you just took. You can see how the look and feel of the subject changes with Shutter speed. Try this experiment with some real subjects like Waterfalls, Birds in flight, Pets running, etc.
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