Shutter Priority mode is represented on your camera dial by the letter ‘S.’ However, some cameras will feature Tv for the same mode, in which case, the Tv symbol stands for ‘Time Value.’ On those cameras, you will also see Av for Aperture Priority mode as a representation for ‘Aperture Value.’
As a review, there are three elements that determine the exposure of a particular image: the lens aperture, the shutter speed and ISO (or sensitivity of the image sensor or film). If you are not familiar with these three elements and how they affect exposure, I encourage you to read the following articles before moving forward.
Shutter Priority vs. Full Auto
When the camera is in Full Auto mode, it uses a built-in light meter to adjust the different elements of exposure for a balanced image. All three elements are automatically set by the camera. In Program mode, this can also be true; however, you gain more control over certain elements (like setting a specific ISO value) and other features like exposure compensation and flash settings.
Shutter Priority mode allows you set the shutter speed to a fixed time (e.g., 1/1000s, 4s, etc.) and let the camera adjust the aperture value, and possibly ISO value, based on how the camera’s meter sees the scene.
Creative Control of Shutter Speed
So why would you want to set a specific shutter speed on your camera?
The most common reason why would use Shutter Priority mode is to control the appearance of motion in an image. This could be to freeze motion or to blur motion.
To freeze motion, you want to set your camera to a faster shutter speed. In sports, this can range from 1/500s to 1/1000s or faster. It calmer situations, 1/60s might be what you need to avoid blur from movement.
If you want to blur motion, set the shutter speed to a slower time, which can vary depending on the speed of the subject. If you are panning as you track a fast motorsports subject, it might be 1/400s (as in the above photo). If it is your kid on a tricycle, it might be 1/15s. In the case of a carnival swing ride, it might be 2 seconds as in the photo below.
As with other modes that give photographers more control, you can use Exposure Compensation while in Shutter Priority Mode. If you add +1EV to exposure compensation, it will open the aperture up an additional stop (e.g., from f/4 to f/2.8) while the designated shutter speed remains the same. Likewise, if you subtract -1EV on the exposure compensation settings, it will close the aperture down one stop (e.g., from f/4 to f/5.6) while the shutter speed remains at your chosen setting. To learn more, read this article on How to Use Exposure Compensation.
Wrapping Up Shutter Priority Mode
The subtleties of using Shutter Priority mode is largely dependent on the subject you are shooting. Generally, this mode is best reserved for sports and action scenarios to freeze motion. If you understand how it controls the camera, however, you can find plenty of creative uses to show motion by mixing elements of moving subjects or moving the camera with a pan and slower shutters speeds.