[stormtech]

And if you want the camera to decide on the best combination of settings to get the best IQ from your Pentax lens, choose the MTF option on your P mode menu item on the camera.

This is probably the best answer - the OP hasn't posted back in this thread - might have gotten scared away by it getting so deeply technical........

My wife uses one of our K-5's, and doesn't want to learn anything more about aperture and shutter speed settings, so I set the "P" mode on "MTF" and let her rip with it!

[sbh]

Thanks to all for your helpful replies, I didn't expect that many!
@Ash, great idea. I usually shoot in manual mode unless it needs to be quick. I could use the P with MTF for a while and observe the settings.
@halfspin, that is interesting since my thoughts are not only about sharpness but also about colour, contrast, DR etc.. So, in this case I would go for ISO 80. But there is still the question wheter it makes a difference having a brighter light with schorter shutter speeds or lower lights with longer shutter speeds. (I can control the light on the subject.)

Let me put it this way: In which "light intensity" does the sensor perform best? We know that he doesn't like low light because there will be noise either due to high iso or very long shutter speed. So if I turn up the light, the image quality gets better due to lower ISO and shorter exposure time. Let's say we have ISO 80 and 1/60 at f8. When I turn up the light, I can correct that with a fater shutter speed. Turning it further up, at 1/250 or 1/500 or even 1/1000 the light would be really intense. My assumption is that too intense light isn't good either, resulting in the question of "the ideal conditions".

I must admit that this is a picky qestion.