Originally posted by rawr The setting you are using (High-speed priority) only applies to P shooting mode.
That and the default behavior for green button in M mode.
I just did a little walk through the feature jungle on my K-3 and discovered that the "fast" program line is most evident when auto-ISO is turned off. Crank the ISO up manually and watch the camera ramp the shutter speed in favor of the aperture.
I have run into this sort of behavior before and it is puzzling until you think of the program line as being defined in terms of EV (
Exposure
Value), that being a look-up table of shutter/aperture combinations for each EV step. It operates independent of the auto-ISO feature and (from my observation) is applied only
after the ISO is set. (Remember that EV is not a measurement of light
per se; rather, it is a way of expressing how much of the available light hits the sensor. It is completely independent of ISO.*)
The camera is generally pretty conservative about bumping ISO unless the available light is pretty dim. In bright conditions the ISO stays low and only a little higher when the "fast" option is chosen. As a result, shutter speeds tend to remain low despite using the action setting. Turn auto-ISO off and crank up the ISO and the action program line comes on nice and strong.
I hope this makes sense.
Steve
* That is EV in the pure sense. Coupling the concept to ISO provides a means to suggest subject luminance. A good example would be camera low-light AF ability which is often expressed in EV. In that case, ISO 100 is the convention, but it is usually necessary to qualify by stipulating the working aperture of the mounted lens (e.g. -3 EV(100) @ f/1.4)