05 June 2014


The DA18-135wr is a lens with its own polarizing filter built in!
No not as it pertains to light, but as a conversation piece.  Most owners think very well of it, and its specs hold great appeal: the first silent DC motor has held up well compared to the perceived woes of its SDM sibling, its weather resistance and range are great to carry as a single unit.  WR does not just work in foul weather, but in many other times when switching lenses isn't a great idea (think dust and sand not just rain-drops).  At the same time, most people point out edge softness as the price of a super-zoom lens, and chromatic fringing as easy to correct with either in-camera or on-computer processing.

All points are fair, and each owner needs to evaluate what it takes to make a lens do well enough for their needs.  I have tried three of the 18-135s and it doesn't work for me.  I sold my most-recent copy and picked up a Sigma 18-250mm the same afternoon, and put some money in the bank (aka 'lens fund').  The compromises required for this lens fit me better, and it's that simple.

What does the Sigma do better?  Well it has more range, clearly enough, and the f/6.3 penalty kicks in right about where the 18-135 stops so fair is fair.  I haven't really tested it explicitly at 135mm but I have the strong feeling it works better than the Pentax lens there.  Why?  Because it outperforms the Pentax at higher focal lengths for color fringing, showing essentially none in spots where the DA lens showed quite a lot.  I am not a fan of correcting lenses within the camera, which made my time with micro-43 gear trying too.  The Pentax K-5 series exacts a time penalty for correcting fringing and distortion at the time of shooting, that's mostly what I dislike.  Both my early Sigma 18-200mm and this 18-250 do not need fringing correction to speak of at any time - sure it can be done and improve things, but only when peeking at a higher level that I enjoy peeking.  Again, it's that simple to me.

I will post some teeny images here to show what I mean, but click 'em to see things better.
hmm, wires look
The dreaded telephone pole/wire shot with +EV correction always outs bad fringers and the Sigma barely flinched at 250mm wide open, which beat the 18-135mm by 160mm± in my experience.  Yes I've lost out on weather resistance, but the Sigma has its HSM motor that is nearly as fast to lock focus (not quite though) and is equally silent.  OK I lost quick-shift manual focus too, and that's a bummer though not as huge as I keep telling myself it should be.  I can definitely detect fringing near the corners, and if I get worked up enough about it I can push a button on my computer.  I probably won't but I can!
250mm f/8 bottom crop 100% - soft w/minimal fringing.
The extreme corners do show more fringing.

And lest we forget, the Sigma can do closeups to 1:2.5, almost half life-size.  I tested it against my Pentax A50/2.8 macro and 1:2.5 is a very good match for scale, but let's be clear the macro prime impressively outscores the superzoom.  When closeups matter the 50 must come along, but when it's incidental to the shooting this zoom will serve well enough in good light.  Funny thing about closeup ratings, Sigma always underrates their zooms: from the 17-70 to the old 18-200 to this one, I can always squeeze out a closer closeup than they claim.  How nice!