Shutter AND Aperture Priority?

Do any DSLRs have the ability to lock shutter speed and aperture while the camera adjust sensor sensitivity as appropriate? Guess you might call it TAv or something on a Canon:)
I was thinking today that they probably would, given what I have heard of high quality images from some cameras at up to ISO 400, and the relative ease I imagine such a feature could be incorporated. I checked the 10D specs though and there didn't seem to be anything like it on that model.
I can think of a few situations where this would be useful. It would be a big advantage over film.
Does this make sense? I've never used a DSLR, so maybe this sounds stupid to experienced digi photographers.

It makes sense but modern sensors aren't that good yet that most people want to shift the sensitvity (ISO) first. Only two Nikon models, the D100 and the D2H, can do this using a custom setting feature called Auto ISO.

With auto ISO on, the camera is programed to adjust shutter speed or aperture before it will begin to adjust the ISO. So go get the ISO to adjust, locking down the shutter, as in Shutter Priority mode is the first step. I this mode, the aperture can still adjust but once it is wide open, the ISO will start to adjust. Since the ISO can adjust between ISO 200 and 1600, this would give you an additional three stops of flexibility.

Using manual mode to lock both shutter speed and the aperture, the camera in auto ISO mode will use the meter to adjust the ISO to compensate as well as it can in its three stop range. This is exactly as you describe.

Since this entire operation depends on the metering to determine the ISO and the noise characteristics at 1600 ISO is much different than 200 ISO, most people keep the Auto ISO feature off and adjust the ISO manually to the exact level needed for the conditions.

Neil Fitzgerald wrote:Do any DSLRs have the ability to lock shutter speed and aperture while the camera adjust sensor sensitivity as appropriate?

Actually yes in a way. The Canon 1D and 1Ds allow ISO bracketing. So you can select manual exposure mode which locks the shutter speed and the aperture and then brackets ISO in whatever way you specify. This is a bit different than what you are asking which would be an automatic exposure mode that leaves the shutter and aperture alone and then just varies the ISO according to a metering algorithm.

I think this is a great thought.

I wouldn't be surprised this happening in the future. Can't imagine devellopers didn't think of this. If you want this send a mail to Canon. They might be able to program it in before their next release tomorrow....(wishfull thinking)

Peter