The K-S1 and the 18-135 lens

Tatouzou wrote:

The TAv mode is very convenient for shooting action: you select shutter speed and aperture, and set Auto-ISO to 100-6400 or even 12800.

This way you can select the depth of field and the shutter speed, whether you want a high shutter speed to freeze everything, or to get a shallow depth of field in bright lighting, or a slower shutter speed to get a blurred background while panning the camera to track the subject. The camera will deal with the exposure, taking into account the EV compensation you have selected, and you can concentrate on framing.

Modern APS-C sensors give quite usable pictures up to ISO 3200-6400 depending the light; and, above, a noisy shot is better than a blurred one.

Sv is for when you want to choose the ISO setting and let the camera choose aperture and shutter speed, like in the film era when shooting in P mode (you could not change the ISO without changing the film). I almost never use it.

On cameras with two control dials, my favorite is P mode with hyperprogram: you can just point and shoot, or change the aperture with the back dial, and the camera switches automatically to Av mode or change the shutter speed with the front dial, and the camera switches to Tv mode. By pressing the green button, the camera switches back to P mode.

Thanks your the explanation. So, with a single control wheel (like what I have on my K-S1), the "P" mode (with the auto ISO) is the most usable. I appreciate its capability to set the optimal aperture, and not to go below 1/60', of course, if it is possible.