I prefer primes for shooting with film these days. Haven't tried the 43 but 50 on dslr is just tad long for me. Have you used a prime before? 43 is a good choice for a first prime, but it doesnt cover everything. I find that unless it's between 28mm to 35mm prime, for a dslr you can't only have one prime (without carrying the zoom around as well) and would crave for a wider lens quite often (I don't usually crave for the long end as much). Don't let this discourage you from getting the 43 though as it's a stellar lens and the FA limited 3d effect totally rolls the Tamron. They probably have almost equal perceptible sharpness if you don't pixelpeep (from the images that I've seen). My first prime was a 50 and it's a great complement to the kit lens.
Having said that I love the 28-75. It's sharp (it's strongest suit?), the lightest and smallest in it's class, and have great colors (cool-ish, almost nikon-like, but the midtones still have the pentaxy pop). and if I can only have one lens from all of my collection for the K100D, this one would probably be the one to stay. (Different story if it's a full frame, I would keep a 50 or a 43)
Of course this depends alot on your use as well. What will you use this lens for?
Last edited by Andi Lo; 05-10-2009 at 09:18 PM.