Originally posted by Truxtar
1. The prime lenses are quite slow (f 3.2, f2.8, f2.4)
2. The autofocus is not fast and has no silent motor (Not that much of a dealbreaker for my purposese I think)
and the most important point
1) Slow compared to what ? I don't know, but when I look on the BH Photo or Adorama website, I find plenty of prime lenses with aperture < 2. Same thing when I look on the used market. If there's something easy to find for the K mount, it's certainly a fast prime.
2) Actually, the AF on the K-50 is as fast or faster than any other DLSR in the same price range. And any difference is in the order of 0.1 sec, which is totally irrelevant in real world operation. The slow AF of Pentax is really a thing of the past. Sure, 20 years ago, there was a noticeable difference in AF speed. It's not true anymore. Unfortunately, many reviewers still seems to be biased toward "slow Pentax AF", even when their own numbers show otherwise. For example, a review of the Canon 70D, a higher end camera than the K-50, in a magazine described the AF as "extremely fast" with AF speed of 0.41s at EV6 and an average of 1.21s at EV -2. The same reviewer described the K-50 AF as sluggish with speed of 0.38s at EV6 and 1.48 at EV -2. Maybe I'm missing something, but based on their numbers, both seem quite similar and, if anything , the "sluggish" just look as speedy as the "extremely fast"... Unless 0.3s in very dim light makes a huge difference to you.
As for the noise, the K-50 certainly has more than competing products which have NO AF motor. So, they're silent, but at the price of only being compatible with motorized lenses. Which, as you may guess, will cost more than a non motorized one of the same quality... On the other hand, the counterpart of having the AF motor in the body is that you have full lens compatibility with any AF lens ever made for the mount. For me, this advantage more than balance the price of having a bit of noise from the AF motor. And this noise isn't as noticeable as some would like you to think. Unless you're looking specifically for the noise, you probably wouldn't be bothered by it.