Originally posted by reivax Not really sure I understand, why wouldn't I want to get used to this type of lens? What's wrong with it? What lens should I be using?
(ssst... it's a conspiracy to keep you from buying a great, exclusive lens...)
There is fast, and there is FAST. There are relatively few f/1.2 lenses, very very few that are faster (and those get mighty expensive). F/1.2 is like at the junction of extremity and afford-ability. Extreme, because they can be tricky to use wide-open; and affordable, because for instance I got a K50/1.2 for US$250 shipped a few months ago, and that's about market rate.
AFAIK there are no AF f/1.2's made for Pentax. That leaves either A-type or M-type MFL's. My K50 is M-type, no aperture automation, so I must use it either wide-open, or in M(anual) mode for stopped-down metering and shooting. So that's 3 degrees of trickiness beyond an FA50/1.4:
no autofocus, and
no auto-aperture, and
thinner DOF. Yes, it takes a bit of practice.
The K and A50/1.2 are both top-flight lenses, literally among the best ever made by anyone. (The auto-aperture A50 is much more expensive.) The micron-thin DOF wide-open and tremendous light-gathering capability allow great effects. Stopped down slightly, they're exquisitely sharp and clean. Ah, that thin DOF isn't unique to 50/1.2's. You'll get thinner DOF from an 85/2 and even the common-as-dirt 135/2.8 and 200/4. But because those are longer, the effects aren't as extreme.
So keep shooting your 50/1.4 at various distances and apertures. Find how your camera-to-subject distance affects the feeling of depth and focus in pictures. After awhile the 50/1.4 will seem almost ordinary... and then you'll lust for a 50 or 55/1.2. Wait, that's not thin enough! Gotta get a 58/1.2!! No, a 50/1.0!! No, a 50/0.9!! Ooh ooh! How far can you go?!?!?