Tv versus Av: Which is the best choice?

Many photographers religioiusly shoot on aperture priority -- Av -- when they are hand-hold their camera. They do this so they can control the amount of depth of field they are getting, and usually they want as much dof as possible. I feel in many instances this is a mistake.

My rationale is that depth of field is irrelevant if the picture isn't sharp. What happens too often is that it's very easy to get so involved in the subject that when you close the lens down for increased dof, you lose sight of what the shutter is doing because it's being adjusted automatically based on your f/stop choice. If the shutter speed gets too slow, the picture will be blurred. At that point extensive depth of field won't matter at all.

I contend that first and foremost, you must use a shutter speed that gives you a sharp picture. This is generally 1/60th of a second or faster unless your subject is moving very fast and/or you are using a telephoto lens. In those cases, you need a faster speed such as 1/250th or more.

Then, and only then, can you decide on how much depth of field you can have. If you are shooting at, say, 1/250th of a second and you decide you want more dof, your only option at that point (assuming the shutter speed doesn't get slower) is to raise the ISO or put more light on the scene.

If you are using a tripod, on the other hand, and your subject isn't moving (like a landscape), then you have the luxury of using apeture priority and choosing a small f/stop like f/22 or f/32. The slowness of the shutter doesn't matter since there is no chance of blurring a subject.

There is only one exception to this. If you are hand-holding the camera and you want the fastest shutter speed possible for a particular situation, then you can choose Av and select the largest aperture on the lens. This, in turn, forces the camera to choose the fastest shutter speed possible given the lighting and given the ISO you are using.