Shutter Priority (Tv) mode
When using Shutter Priority (S or Tv) mode, you choose the shutter speed and the camera automatically chooses the lens aperture that will give the correct exposure.
Shutter Priority mode is particularly useful when you want to control the amount of movement blur that appears in your shots. To freeze fast-moving action in a sports shot, for example, you’ll need to select a fast shutter speed.
When you use this setting, there’s a risk that you might accidentally overstep the available aperture range. If this happens, the camera may display an alert, but will still take the picture (which will end up looking under-exposed).
Some models have a ‘safety’ option, which will restrict the shutter speeds available in particular conditions to prevent this.
Similarly, if you choose a shutter speed so low that the camera can’t select a lens aperture small enough, it will either take an overexposed shot, or restrict the shutter speeds available to you.
Paradoxically, if you want to shoot with the fastest shutter speed possible under the conditions, it’s better to switch to Aperture Priority (A) mode and choose the maximum aperture. The camera will then select the fastest speed you’ll be able to achieve in the conditions.
Shutter Priority mode is best when you want to create movement blur. It’s useful for panning shots, where the subject shows up sharply against a blurred background (try shutter speeds in the region of 1/60sec to 1/250sec), for blurring wheels or limbs to show movement (try 1/15sec to 1/125sec) or to give moving water a silky sheen (1/4sec to 2sec or longer). In each case, make sure the camera can select a suitable lens aperture for correct exposure.
You can access the Shutter Priority mode by moving your camera’s mode dial to the S or Tv position. You then need to half-press the shutter release to activate the exposure metering system. Now rotate the camera’s Command dial while watching the status panel or the LCD.
Depending on the camera model, you turn the dial either clockwise or anti-clockwise to increase or reduce the shutter speed.
You’ll need to use a tripod for shutter speeds of 1/30sec or longer. This minimum shutter speed is higher with longer zoom settings.
Safe shutter speeds
No one can hold a camera perfectly still, and the slower the shutter speed, the greater the risk of blurring from camera shake. It can be dangerous to generalise, but there’s a rule of thumb for working out safe shutter speeds.
It’s based on the equivalent focal length you’re using. The 18mm wide-angle position on the kit lens will correspond roughly to a 28mm lens on a ﬁlm camera and the 55mm position corresponds to approximately 85mm in film camera terms (this doesn’t apply to full-frame DSLRs, where no conversion is needed).
Simply take the reciprocal of the equivalent focal length to find out the minimum safe shutter speed. So at the 18mm position this would be 1/27sec (the nearest equivalent is 1/30sec), while at the 55mm position it would be 1/83sec (1/80sec or 1/90sec is the nearest).
PAGE 1: Digital camera modes explained – Program Exposure mode
PAGE 2: Digital camera modes explained – Aperture Priority mode
PAGE 3: Digital camera modes explained – Shutter Priority mode
PAGE 4: Digital camera modes explained – Manual mode