Originally posted by UncleVanya Enjoy your 70 for now. There’s no need to charge too much at once.
I agree, and that HD DA 70mm Ltd is such a compact wonder, and a wonderful performer. It can provide fine edge-to-edge sharpness, right from its f/2.4 aperture! That is rare right there!
As far as I know, the new Pentax DFA 100mm is a WR macro lens, but still retains the screw-driven AF. Its goal design was to reduce purple fringing under lighting where this can occur. It is well constructed, much like a "Limited". But I have the previous DFA 100 WR macro, and it too looks and feels much like a "Limited", and is very sharp.
As to the DA 21mm Ltd, it is a very compact, good walk-around prime lens with a versatile FL for this purpose. However, since getting my HD DA 20-40mm Ltd, with its superior AF, faster f/2.8, and WR construction, I find I use the 21mm prime far less often.
As to the tele zoom choices, the HD DA 55-300mm f/4-5.8 WR both you and I now have, holds up extremely well to examination, depending on one's specific needs. Of course, the PLM version's AF is considerably faster, although mine has gained noticeable speed on my KP compared having it on my K-5 IIs or K-S2. Its slower AF speed is due in part to its longer focus rotational throw, but this can actually be an advantage for MF fine tuning when setting the camera for MF or for AF override for MF when using the "quick shift" feature.
As to imaging performance, it is quite close between these lenses. I suggest doing a google search for the HD DA 55-300mm f/4.5-6.3 ED PLM WR RE review, and locate the review by ephotozine, an English testing group, I believe. In this review unfortunately, the graphs are not shown, but they give in-depth commentary describing their findings. Then a link is given so you can click to bring up the previous model right away. They give extra points for the PLM AF and its bringing a major improvement for video shooters. Very important for some.
We know with even fine zoom lenses performance is typically reduced as it is zoomed to the longer FL, especially at the edges, and these lenses are no exception- but they do better than most, and with tele the edges usually become yet less important when going towards the longer end. It is interesting to note the newer PLM is given a "very good" rating centrally right from wide open, but the previous HD WR version was tested not only at excellent, but at "outstanding" centrally, which is the only version reaching this level at any point. That and excellent ratings hold up until going into the longer FL range. Edges hold up a tad better at the longer end by the PLM version, but this is where that becomes less important. The older lens isn't internal-focusing, so it does not have "focus breathing", thus can provide a larger image at moderate distances. The PLM has a better rep for bokeh, but my older lens has given me many shots with satisfying bokeh. Its faster aperture could help with a bit more blur as well. Each of these lenses have advantages, depending on the uses they are put to. For me, the one I have is very fine, and I have no intentions of replacing it with the PLM version.