Canon DSLR tutorial: When should you use the Tv mode?
Av (Aperture Value or Aperture Priority) mode is great for shots in which you want to control the depth of field by selecting a particularly wide or narrow aperture setting, or want to select the ‘sweet spot’ of a lens – this is the aperture at which a lens delivers its best image quality, typically around f/8. Av mode is therefore well suited to portraiture and landscape shooting, but there are situations where it’s better to use Tv (Time Value or Shutter Priority) mode instead.
As its name suggests, Tv mode enables you to set the exposure time, or shutter speed. For example, you might want to set a very slow shutter speed of 30 secs to create light trails from moving vehicles at night, or several seconds to blur water as it cascades over a weir or waterfall. For panning shots of racing cars or motorcycles, a shutter speed of 1/60 sec to 1/125 sec works well, as this will enable you to capture motion blur in the background, especially when you’re using a long telephoto lens. At the other end of the scale, you may need a fast shutter speed of 1/1000 sec or higher to freeze the action in sports or wildlife photography.
In each of the above cases, the Program mode may well serve up a shutter speed and aperture combination that’s not ideal for the task. By switching to Tv mode, you can manually dial in exactly the shutter speed that you want to use, and the camera will adjust the aperture accordingly. One thing you need to watch out for, however, is that the shutter speed you set doesn’t require an aperture that’s wider or narrower than the lens is capable of in order to give a correct exposure. For example, let’s say you’re using an EF-S 18-55mm f/3.5-5.6 lens, shooting outdoors on a gloomy day. If you were to set a fast shutter speed of 1/500 sec, even the widest apertures through the zoom range (f/3.5 to f/5.6) wouldn’t be enough to produce a correct exposure; instead you’d get a badly underexposed image. Keep a lookout for a blinking aperture display in the viewfinder, or on the camera’s rear LCD, which serves as a warning. A handy tip for low light situations is to select Auto ISO. This will bump up the camera’s sensitivity setting by just enough to enable a correct exposure within the lens’s aperture range, at higher shutter speeds. Even so, in very dull or indoor conditions, you may need to set a slower shutter speed in order to get a well exposed image.
For night shots, you will need to use extremely slow shutter speeds, keeping the shutter open for more than 30 seconds. This option isn’t available in the regular shooting modes, including Tv mode, so you’ll have to switch to Bulb mode instead. On some cameras, such as the 60D and 7D, Bulb mode is available as a separate shooting mode, selectable via the mode dial. In other cameras, you’ll need to set up Bulb exposures via the Manual shooting mode.
What shutter speed should you shoot?…
Setting your shutter speed to 30 seconds for night shots gives a sufficiently long exposure to make watery reflections mirror-smooth. Another bonus is that people walking around within the scene will blur into invisibility. You’ll need a sturdy tripod to eliminate the risk of camera shake.
A shutter speed of around 1/15 sec should enable you to capture sharp handheld, wide-angle shots of static indoor subjects, such as this museum exhibit, without the need to use a flashgun (which may not be allowed). You can stretch the exposure to about 1/4 sec if the lens features image stabilisation.
For moving subjects, you’ll need a fairly fast shutter speed in order to freeze the action. For this shot of a skydiver we’ve used a shutter speed of 1/500 sec, which is generally also fast enough to freeze the motion of people walking or running about, dancing or playing most sports.
For very fast and erratically moving objects, a shutter speed of 1/1000 sec or higher will be needed if you want to get everything in shot pin-sharp. Notice here how not only the boat is sharp, but also the tiny drops of spray thrown up from the water. You can use a slower speed if you’re panning to follow a subject.
This entry was posted on Friday, August 9th, 2013 at 4:10 pm and is filed under Canon D-SLR Skills, Photography Tutorials. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a comment. Pinging is currently not allowed.