Originally posted by Timotis77 Any thoughts of longer focal lenghts? 50-200? 55-200? 55-300??
No question: get the
DA 55-300mm f4.5-6.3 PLM if you can. (About $500 new when on sale at DCXpert; hard to find used, but expect to pay about $350-400.) It is a bit heavier than the DA 50-200 (440g v 285g) but it retracts to a very compact size. The extra reach is invaluable, particularly for wildlife, but also for kids, pets and sport. It has the fastest and quietest autofocus of any Pentax lens. WR and HD coatings.
To me, the greatest surprise with the PLM (apart from the amazing AF) was the image quality: the colours, microcontrast and bokeh are in the top echelon of non-Limited and non-star Pentax lenses.
Very good resolution across the frame at the wide end when stopped down, which makes it a very good landscape lens.
(Stitched pano)
Good centre resolution at the long end, even at 300mm and even wide open, which makes it a good wildlife/sports lens.
See some fine examples here:
HD Pentax-DA 55-300mm F4.5-6.3 ED PLM WR RE - Show us what it can do, what it CAN'T! - PentaxForums.com
Slowish aperture, particularly at the long end (f6.3 above about 270mm), although you can get f5.6 by backing off a little, which helps focusing in low light.
The step up from there in a tele zoom is the
DA*60-250 f4, but it is heavier and quite a lot more expensive. It offers a wider aperture, which should in theory be better for wildlife (and allow the use of a TC), but user reports say that its utility for wildlife is limited by the slowness of the SDM focus and the focus breathing (which reduces the effective magnification).
The step up from the PLM in a wildlife lens is the
DA*300mm f4, preferably paired with the DA 1.4x TC. It see that as complementing rather than replacing the PLM.
The step down in price from the PLM in tele zooms are
the older Pentax 55-300mm f4-5.8 models with screw-driven AF (all now out of production). There are three variants: DA-L (plastic mount, no QS), DA (adds metal mount and QS), DA WR (adds WR and HD coatings and a nicer build). They are optically identical, except for the HD coatings on the WR version. I used to have the DA-L and as a bargain buy ($100-150) it and the original DA model are hard to beat if you get one in good condition. (Bear in mind that many older ones will have wobbly barrels by now.) You might find a newish copy of the HD WR version for around $300-350.
Resolution is as good as the PLM when stopped down, maybe even better at the long end. The microcontrast, colours, bokeh, control of CA and overall rendering are pretty good, although not in the same class as the PLM IMO. (More prone to nisen bokeh in particular.) It's similar in weight to the PLM and takes the same size filters (58mm) but doesn't retract so is bulkier to carry. Longer MFD than the PLM (1.4m v 0.95m) but similar maximum magnification. The autofocus seem noisy and slow after using a DC or PLM lens.
I had a great run from my DA-L 55-300 f4-5.8 for the small layout:
More samples here:
Pentax DA-L 55-300mm f4-5.8 sample images - Des(Australia) - Flickr
I haven't used any of the
DA 50-200 lenses. You should be able to get even the WR version quite cheaply. It's very compact and lightweight. I've seen some very good images with this lens, although it doesn't rate highly in reviews.
The question I'd ask is, given you have the 18-135, is it really worth carrying a separate zoom just to get 135-200mm f5.6? Often 200mm wouldn't be enough for wildlife anyway and having 135-200mm f5.6 wouldn't add anything special in aperture or perhaps in IQ. (If you were talking about a DA*200 f2.8 or 70-200 f2.8 it might be a different story - either would bring something in aperture and image quality.) For a slowish tele zoom, the 55-300 adds much more versatility than the 50-200 without a lot more weight or bulk.
The 55-300 (particularly the PLM) also makes an excellent companion to the 20-40. Lately I've been using the
DA 15 Ltd, DA 20-40 Ltd and DA 55-300 PLM with the KP for a compact light-weight and high-quality travel kit. The 55-300 holds its own even in that esteemed company.