
Originally Posted by
Charles Glatzer
Jay and others,
In Manual priority you make a cognitive decision, first deciding which variable aperture or shutter speed is most important, setting that first into the camera before adjusting the other variable to render the correct exposure. The only difference in Av or Tv from Manual is that the camera automatically adjusts the variable you do not. Av you select the aperture of choice, with the camera selecting the other variable, shutter speed in this case. In Tv you select the shutter speed of choice, with the camera selecting the other variable, aperture in this case. Regardless of the priority used the resulting exposure should be one and the same, determined by the Meter Pattern in use not the Priority. Why would I choose an auto priority (Av/Tv) that is going to more than likely deviate exposure every time I move the camera position or zoom a lens, when the light falling on the subject is constant?
Best, Chas