Originally posted by sany Can somebody help me explain a little bit about this so as to make me realise how lucky I am - the thought running in my mind is - aren't there old lenses that can be used for canon and nikons then?
Yes, but I would argue that this is missing the point.
In Pentax's heyday, they were a top-notch brand with a lot of industry respect. Their M42 mount, and early K-mount lenses, were in direct competition with lenses produced by Zeiss, etc. A SMC Takumar (or SMC - K mount) 50mm f1.4 is an absolute steal at the price, and being able to mount them on a modern DSLR (with such ease) is *not* possible with Canon or Nikon. It is possible with some other brands, but they would be just as "obscure" as Pentax.
Optical technology has not really progressed *that* much in the last 50 years. Camera body technology has. You can get absolutely phenomenal results with a K 24 f2.8 and the K5, or one of the old 50's, or one of the old 85s.
Pentax is also one of the only modern companies that will produce an old-school, full frame, autofocus lens like the FA 77.
Really, pentax is about the primes. And it's not for people who love auto-everything. I'm happy my first camera purchase was a Pentax, because the plethora of old, good lenses (ahem K55 f1.8) forced me to actually learn photography.
I recently went of a trip and rediscovered how manual focus can be far superior to autofocus. And I was using a 50 dollar lens. This is the joy in using Pentax. It's a system for enthusiasts. I wouldn't bother with it if people were paying me to take pictures, but as a hobbiest, I can't think of a single better bang for the buck (and fun) system to use. Pentax is also notable for actually caring about how a camera "feels". Ergonomics are a strong suit of Pentax (with Nikon, and especially Canon, lagging far behind in my worthless opinion).
I mean, you can look at the DA 40 on paper and think "why bother?"... but when you use one, you will understand.