I have two of these lenses, and there's no sign of any problems with the glass. I bought the first one used a few years ago, and was pleased with the image quality, less so with the build quality. The zoom ring became a little loose over time, so I looked for another lens at a good price.
A few months ago, I saw the FA28-70 f4 on sale at Lens and Shutter here in Victoria (BC, Canada) for $199 Cdn, so I bought one, keeping the first one as a backup. The new one is nice and tight, and takes great pictures. I'm aware that there's a certain amount of distortion at the wide end. I had to crop one of my favorite photos to eliminate the curving ceiling/wall joint. Now, if I need a sharp wide-angle with almost no distortion, I use the FA20-35 f4. Having said all that, what's the attraction of this lens? Several things: it's inexpensive, compact and light, it has a focal range that's really good for everyday use, it produces sharp pictures, and, fairly important to me, it has a constant aperture. I often shoot with studio flash and my MZ-S, and a variable-aperture lens would be a big headache. For over 90% of my studio work, I need only two lenses, the FA28-70 f4, and the Sigma 70-200 f2.8 APO. Just set 'em and shoot. If the FA28-105 f3.2-4.5 was a constant f4, I very likely would have bought it instead, or maybe the FA24-90 f3.5-4.5. but they're not. Pentax, can you hear this? Pat White
