Which lightweight lens?

I have a 16-50 DA* and it is great, just heavy and large for some situations when I really want to travel lite and it gets in the way of the pop up flash.

I also have a 18-200 Sigma and, though it is OK, results are just not that hot.

I have an old FA 28 to 70 which at f4 is a great lens, light quick and good focus accuracy, however, it is not wide enough for general use.

I also feel that my screw drive lenses are faster at focusing than my SDM lenses.

So, what would you guys go for (new or older) to give me a lightweight (both on the back and purse!) option?

Is the 17-70 worth the cost. Anything I should watch out for getting a second hand one of these?

What about the 18-50WR lens?

Why not buy a 40mm DA and learn to 'see' with it? Fast, light, sharp, discrete and you can always take a few steps forwards or backwards

Some day I want a 43mm ltd, I already have 2 50mm 1.4s so really after something a bit different. It needs to be zoom.

If you just want a lighter equivalent to the DA*16-50 I think you could consider a DA16-45. It is of course only F4 and is a screw drive lens but, although getting a little harder, can still be found new at reasonable prices.

I have had some bad experience with SDM failures (My 3rd DA*16-50 has just come back from a warranty repair). I have therefore resolved not to buy any SDM lens 2nd hand, including the 17-70. I would want a full manufactures warranty period on any SDM lens.

Glyn

The 18-55mm and 50-200mm WR zooms are excellent and are also light and compact.

The Pentax 17-70 has a very good reputation, the only things stopping me from buying one are the lack of weather sealing and the SDM (though the DA*50-135 is likely to severely test my SDM aversion at some point). As alternatives you could consider:

Tamron 17-50 (still f2.8 and reportedly lightish for an f2.8 standard zoom)

Sigma 17-70 OS
*About £120 cheaper than the Pentax
*Faster wide open (f2., and no slower at any point in the range (slowest is f4)
*Uses Sigma's HSM, rather than Pentax SDM. This is generally reliable: so long as the lens isn't front/back-focusing when it arrives (in which case most reputable vendors pay return postage), there are very few reports of Sigma HSM failing.
*Has Sigma's in-lens OS. This is reportedly quite good, and if you don't like it you can always turn it off and use the camera SR (NB: Don't use both at once).

I'd say to go for the 18-55mm. It's the only lens I own wider than 28mm, and you can't beat it for the money.

I did think about that one too, but the OP said that his 28-70mm wasn't wide enough. Personally I like the F 35-70mm as a walkabout lens, it gives you something close to the old 50mm at one end and a useful short telephoto at the other.

If you want a smaller lighter lens to supplement the DA*16-50 then the DA18-55mmWR would cover your needs without costing much.

If you wanted to replace your DA*16-50 then the DA17-70 makes quite a lot of sense as it is a bit smaller and lighter and has usefully longer reach. Unless you really need f2.8 and WR it makes an excellent sustitute. The Photozone review concluded "The Pentax DA SMC 17-70mm f/4 AL [IF] SDM is undoubtedly the most desirable standard zoom lens in the current Pentax lens lineup."

I sold my DA*16-50 and replaced it with the 17-50 and have not regreted the change. As regards the reports of SDM failure I get the impression that this has not been a problem with the 17-70.

Archie

As I already have the FA 28-70 and really like the lens, the 35-70 would not cut it for me.

The sigma is a very good idea and I might try to get a hands on with one. I must admit, I am liking the sound of the 18-55wr more. I has the 18-55mkI lens with my K10 and used it a bit on the K7 but now my nephew has that lot!

My 28-70 compliments my Tamron 75-300 which I find very useful on account of the 1:2 macro setting at the 180-300 range. It really is just the wider end I miss and I could easily just carry the 18-55 and 75-300 to travel light.

I'd recommend either the Sigma 17-70 or the Pentax 17-70 having owned both, the Pentax bettering the Sigma for colour/contrast whilst been pretty much the same regarding sharpness. I haven't owned the WR version of the kit lens so can't comment on that one in particular, I do find the Pentax/Sigma 17-70 a significant improvement over the 18-55 I owned some time ago though.

Simon

Big fan of 16-45. The 18-55 is great, but does vignette.

At £65 from SRS, I had to give the 18-55 WR a go!

I did look at the Sigma 18-125 though!

Thanks for all the suggestions.

I vote for the 35-70, I actually regret selling mine.

I use film too regulary to buy too many DA lenses, so my one and only Pentax zoom lenses are the DA*16-50 and SA12-24 which are the main lenses for the K20D.