What is Shutter Priority Mode?

On most cameras, you’ve got a handful of automatic of semi-automatic modes. One of those is usually Shutter Priority Mode. It’s usually identified with the Tv label on the settings dial. It might also be labeled simply with a “T” or an “S”.

In shutter priority mode, you select a shutter speed. The camera then automatically chooses an aperture value that gives you the proper exposure. This might be a good option if you want to control the amount of motion blur in the picture – choose a slow shutter (i.e. 1/30th of a second) and you can force the camera to capture a little blur. Choose a quick shutter (i.e. 1/250th of a second), and you’ll eliminate most of that blur.

This can, however, be problematic. The aperture value that the camera chooses is restricted by the maximum aperture value of your camera. Let’s say you’re at a night football game. To get a proper exposure, you’ll need something like 1/250th of a second, f/2.8, and ISO 1600. You don’t necessarily know this; you just know that you want a shutter speed of 1/250th of a second. So you flip the dial to shutter priority, set the shutter speed, and start shooting.

If you have a fast lens (i.e. a f/2.8 70-200mm zoom), you’ll be ok. If, on the other hand, you’ve got a slow lens (like a f/5.6 55-250mm, you won’t be in such good shape. The camera will want to set the aperture to f/2.8, but the lens only opens up to f/5.6. As a result, all of your images will come out about 2 stops underexposed (i.e. really, really dark).