[justtakingpics]

I am still lost. I know what Av, Tv, and P do. I understand why they do what they do and exposure, shutter speed, etc. What I don't get is why you have a separate function for P. If I adjust either setting in P the camera selects the corresponding value. Is P for setting both of them manually if I need to whereas I can only set one of them with Av or Tv?

In other words, Av always selects the corresponding shutter speed and Tv always selects the aperture setting and I can't change that but P selects both of what it thinks (just like the other two) but I can change both settings and override what the camera thinks on both settings instead of having to accept the corresponding setting.

thanks to all who have responded.

[SpecialK]

P selects both of what it thinks (just like the other two) but I can change both settings and override what the camera thinks on both settings instead of having to accept the corresponding setting.

Then you are no longer in P.

[Marc Sabatella]

I am still lost. I know what Av, Tv, and P do. I understand why they do what they do and exposure, shutter speed, etc. What I don't get is why you have a separate function for P. If I adjust either setting in P..."

In "classic" P mode, you *can't* adjust either setting. The camera picks both aperture *and* shutter speed, and all you can do to affect the results is apply exposure compensation. there is no way to directly tell the camera what aperture or shutter speed to use.

However, it is try that *some* cameras allow you to quickly change from P to Av mode or Tv mode just by turning a dial. At that point, you are no longer in P mode, really - you're in either Av or Tv mode. So in that sense, P is a mode that allows to either not have to select anything, or temporarily switch to Av or Tv modes quickly. And on these cameras, there might be little point in using Av or Tv, except that if you know you really want Av all the time, might as well just set it there rather than having to keep temporarily switching from P to Av.

[HGMonaro]

What I don't get is why you have a separate function for P. If I adjust either setting in P the camera selects the corresponding value. Is P for setting both of them manually if I need to whereas I can only set one of them with Av or Tv?

With P you can only change one. The camera selects the other value required. It just so happens that because the camera has two wheels, they let you use one wheel to alter aperture and one shutter speed (further confused by the fact that the let you change the funcionality of the wheels as well... but lets ignore that for the moment!)

It's best to think of it like Marc describes, with the addition of, a quick press of the green button puts you back into P mode.

[Rondec]

Think of P mode as a completely auto mode. The difference between Pentax and other camera makers is that they have what they call hyperprogram. This means that the camera will allow to you to change the aperture with one wheel (basically dropping you into Av mode) or the shutter speed with the other (dropping you into Tv mode).

It is only at the starting point that you are truly in Program mode, the rest of the time you are in what Pentax calls "Hyperprogram." Anytime that you want to return to program mode, you just hit the green button and it will put the program line back into place.