Originally posted by Andi Lo
IQ wise yes but to be considered pro gear, DA* have many weaknesses, biggest of which being SDM, and the rather slow focus -both may have been remedied though, haven't followed too closely since I decided to stay away from anything SDM 3 or so years ago. I just remembered that these days we have the SDM screwdrive hack, which is really awesome, but having to buy an old camera in order to hack a lens doesnt seem pro to me.
IQ pentax lenses that exist is indeed equal to canikon's equivalents, but there are WAY more options in canikon, which may suit some pros better. eg Canon 17mm/24mm TS, Nikon 14-24, LOTS of UWA flavors outside the usual f/4-ish 8-24mm lenses, and primes in many FL (not just 50 and 70) that go down to 1.8 or even 1.4. OTOH they dont have anything close to DA lims though, so it's more of a "choose the brand that have the lens you want"
DA limited have really special qualities that I adore but imho more of an enthusiast lens. They have excellent qualities but for the price it's really slow. Most pros dont really care about gear size as long as it's still manageable. Most dont care much about "pixie dust" either (which DA 15 and FA 77 have in spades imho), as long as it works.
My 16-50 died with no warning on me a short while back, but luckily I had an old K20D that allowed me to hack the screw drive because I really didn't want to spend a couple hundred dollars on repairing a motor that could break at any time. The slow AF of Pentax lenses used to not bother me much, but once I started shooting more and more photojournalist-work, the inconsistent/slow/lock-resistant AF on my K5 really annoyed me. I had it on shutter release priority, which helps, but it was still something that annoyed me immensely.
But again, Nikon doesn't really have any pixie dust lenses afaik. I've the 14-24 and it works spectacularly - tack sharp and mindblowingly wide - but I'd love to have the FA77 on my D800.