Figure 2: Command Dial
ing. The primary advantage of P mode over full auto mode is that in P mode you can use the Main Dial to shift the relative values of the shutter and aperture selection. This is called Program Shift and it provides a way for you to bias the exposure towards faster shutter speeds or smaller apertures while the camera insures accurate exposures. You can also use the Quick Control Dial (QCD) on the camera back, to bias the exposure up (lighter images) or down (darker images) depending on the effect that you want. This is called Auto Exposure Compensation (AEC), and is only the ambient exposure bias. It does not effect flash exposure.
Tv is for time value mode, also called "shutter priority." You set the shutter speed with the Main Dial, based on the need to freeze action or portray subject movement or simply for hand hold ability. The camera then selects an appropriate aperture for correct exposure. While in Tv mode you can also use the QCD to change the exposure up or down (AEC). This is only ambient exposure bias and it does not effect the flash exposure.
Any shutter speed can be set between 1/4000 second to 30 seconds. Below 30 seconds the shutter goes into Bulb mode where it will stay open as long as you hold the shutter button down or until the battery goes flat. The remote controller, RC-1 and the remote switch, RS-60E3 both have methods to manually hold the shutter open as long as you like.
Av is for aperture value mode, also called "aperture priority." You select the aperture with the Main Dial, based on the need to limit or expand depth of field/focus, and the camera selects a shutter speed to provide the proper exposure. Av mode can also be used when you want to select the fastest shutter speed possible and still maintain proper exposure in changing light. To do that you just set the aperture to the largest setting
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