How to use Tv Mode: Shutter Priority
In the most basic sense; Tv mode or Shutter Priority is the mode in which the camera selects the lens aperture to acquire a defined exposure in accordance with a user selected shutter speed.
When to use Tv mode: Shutter priority is a mode I rarely use. Shutter priority is for a user who wants to control the shutter speed, and allow the camera to select the lens aperture for them. This means, if a user wants to have an extended exposure, they can select anywhere from 1/4000th to 30 seconds for their exposure. The camera will in turn, select an aperture to prevent an over or under exposure if the lens is capable of achieving the aperture needed to meet the users selection.
Basics: The camera you purchase have various shutter speeds, more professional cameras have 1/8000th of a second, and the more entry level are typically 1/4000th of a second maximum shutter speeds.
A shutter speed of 1/500 or faster (1/1000, 1/1500, etc.) are excellent for “action stopping” images. When shooting sports, the faster the better, the image is captured with as little movement from both the subject and the photographer.
To hand hold your camera, you will need to remember that a shutter speed of 1/(focal length x crop factor of camera) is necessary. If you have a Canon XSi and a 200mm lens, you will need 1/(200×1.6) = 1/320th of a second minimum to hand hold your camera and take a shot. Anything less, and camera shake will likely become a factor and ruin your photo.
That is where tripods and monopods come into play, they allow you to use slower shutter speeds and retain image clarity by removing camera vibrations and movement. For any extended exposures, including night shots, a monopod or tripod become a necessity.
Intermediate: This mode is only useful while you are learning the basics of SLR photography. You are better served using manual mode so that you can select both your desired depth of field, and the shutter speed you believe you will need to get your exposure.
In bright day light, you will need to use fast shutter speeds, or for extended exposures you will need to use neutral density filters, which block light. The classic image of a water fall in day light running, often uses a neutral density filter to prevent over exposure yet allow water movement to create the image.