First I don't believe true "pros" use Av all the time... Or any other particular exposure mode, for that matter.

The most experienced shooters (be they pro or amateur) will use the best exposure mode for the situation... period. That might be M. Or it might be one of the various auto exposure modes.

I have to laugh at folks who "only use M". No one should be wedded to one particular exposure mode and refuse to use others. There isn't a "right" mode to use all the time. The shooting situation often dictates what mode should be used.

Years ago, I shot with strictly manual cameras. Then along came auto exposure. Some cameras had only shutter priority. Others had only aperture priority. It wasn't until the late 1970s that cameras started to be produced with both. Program came along later. Many experienced shooters were suspicious of new-fangled technology at first, stuck in their old methods. But each mode has it's uses.

Use M or Manual when lighting conditions are steady and there is no reason or need for the camera constantly to adjust itself When it's possible to use M you can eliminate the problem of the reflective metering system of the camera responding to subject tonality. M puts you in control of all the settings (using Auto ISO with M gives up that control... see below). But it really isn't possible to always use M, either. Shooting rapidly in changing conditions can very often make it necessary to use one of the auto exposure modes.

Aperture priority mode is most useful when you want to control depth of field, but need to let the camera adjust for variable light conditions.... such as the subject moving in and out of shadows, or different subjects being shot, or when the intensity of the light source itself is changing frequently. Intermittent clouds might be the cause of the latter condition, among others.

Aperture priority mode may be the best choice when working with long lenses that have shallow DOF. Or when shooting portraits and wanting to induce some background blur. Or, for that matter, it might be the choice for landscape shooters wanting to maximize DOF.

Shutter priority is the mode to use when depth of field doesn't matter as much and you want to be sure to stop movement (faster shutter)... or to blur it (slow shutter). Sports photography might call for shutter priority mode.

I'll even use P or Program occasionally... such as when I just need to make a quick shot in radically different lighting conditions and really don't have time to calculate any of the factors. It's sort of the "hail Mary" of exposure modes. An example might be after working indoors, needing to quickly go outside to snap a quick shot or two, no time to fiddle with the settings. Also using a different modes preserves the settings I've been using indoors, so I don't have to recalculate things when I return to shooting that.

Auto ISO is a relatively new exposure mode that's only been available on digital cameras. For obvious reasons, this was never an option to use with film cameras. It really is just yet another auto exposure mode. If you use it in conjunction with M you are not shooting manual exposure... you are still shooting auto exposure and relying upon the camera to figure things out for you. And, IMO, it's very risky to use Auto ISO in conjunction with any other auto exposure mode (that's sort of auto-auto... who knows what will happen!?)

The cameras I use that have Auto ISO do not have Exposure Compensation that works with it. Some newer models do. But because mine don't, I never use it. Exposure Compensation is essential when using any sort of auto exposure mode with a reflective metering system. It is rare that Auto ISO would be needed... I can see there may be times when it would be desirable to lock in both aperture and shutter speeds in variable light conditions, though I really don't have much problem locking down one or the other and just keeping an eye on the second parameter. Another important thing with Auto ISO is to be able to set a max ISO that the camera will use.... and maybe a minimum ISO, as well.

But, I can change ISOs on the fly really quickly, so really don't find much need for Auto ISO. Av, Tv and P pretty much fulfill all my auto exposure needs.

In summary, I probably do use Av mode most often. I use M nearly as much and Tv mode a little less. I only occasionally use P mode and practically never use Auto ISO I often read posts about Auto ISO, hoping someone will illustrate good examples where it might be more essential.... But haven't yet seen a really good argument for using it, where it would be necessary to "get the shot".

The shooting situation decides which mode can or even must be used. Sometimes you have a bit of flexibility about which you can use... Sometimes you don't. But there is not one mode that's better than all the others and usually one or the other will stand out as the preferred mode, at the time, that will make it possible to get the shot you need or want.

Try shooting stage shows, indoors, with accent lighting, spot lighting, bright and soft, with actors dancing and jumping around, using, 'M'. You will be adjusting more than shooting.

I have to keep one camera set for the bright spot and subject motion (using 'M') and another MOSTLY set to 'S' (sometimes the 'effects' work better) to try to get a decent shutter speed and trust the camera to find me the best of the rest. USUALLY works. Vinny

:)

OOOps, I think amfoto1 was for this reply. Sorry (damn buttons get in the way) :lol:

I know you meant amfoto1, but I generally agree with him. When I'm shooting in the circumstances you describe, which is fairly often, I move between manual and aperture priority. In those circumstances I often use spot or partial metering along with either my 30mm f/1.4 or 18-35mm f/1.8 Sigma lenses. Of course, keeping the shutter speed fast enough while pulling in enough light is always a challenge, and I try to keep the ISO on my Canon 60D no higher than 800, although sometimes I have no choice and must go higher.

This may be your experience, but it certainly doesn't apply to everyone. I used manual, with a hand held light meter, for years - before cameras had batteries. Then I used manual with an in-camera match-needle light meter. It wasn't until 1988 that I got a Nikon film camera that had automatic exposure. What a thrill that was to set the aperture and let the camera figure out the shutter speed, or the other way about. There was no auto ISO - the camera read the ISO off the film canister. I, for one, have tried manual and I'm not going back, except in special circumstances. For example for birds in flight I set my exposure off a grey card because I want the birds properly exposed and I don't care about the sky. Different strokes for different folks.