Sigma 18 - 125 @srs

Just noticed this lens is now in stock at SRS.
http://www.srsmicrosystems.co.uk/3120/Sigma-18-125mm-F3-8-5-6-DC-HSM-Lens---Pent...

It has a superb review on photozone under the Canon section and the 15mp area. Anyone used one ?, will it be as good as the 17 - 70 but with the bonus of extra reach ?

Wow, it is available online in Pentax fit without OS, but your right,seems to be a non starter.

Well it's listed on the sigma site as available for Pentax link

I've got them in stock - no web guru issues this time....!

Phew, thank goodness,are you able to tell us how good it is ? does it match the 17 - 70 ?

The previous Sigma 18-125 was not highly regarded in terme of IQ - so if it is optically the same I would avoid it...

There is a Photozone review for it done with a Canon 50D which is very very good,
http://www.photozone.de/canon-eos/407-sigma_18125_3856os_50d

obviously the K200D would resolve less, but if there were any glaring flaws they would show up. It is not the same lens as the earlier Sigma 18 - 125.

Typical for a superzoom, from that Photozone test, it looks relatively soft at the long end. You have to decide whether the convenience makes up for that, and if the price is reasonable enough.

The Pentax 18-250mm is a very respectable general purpose lens.

But the Photozone review shows it having severe barrel distortion and vignetting at the 18mm end, worse than its Tamron counterpart in the Canon test ?

We're not using the Canon version....you can't compare unlike things.

In normal use there is no excessive vignetting and in any event this would be a good thing in some respects. Slight vignetting at wide angles, like slight barrel distortion, is actually very acceptable. Unless we are shooting architectural subjects of course.

In the darkroom "darkening the corners" of a print was normal practice as it helped to darken the sky and concentrate the viewer to the centre of interest of the image. Ultra wide angle lenses often accomplish this for us, such as the SMC Pentax 15mm f3.5 which darkens skies nicely on film without the need for a polariser. It's technically a defect, but pictorially very useful.

Don't worry too much about these internet tests - they test using test targets and rulers and so on, but those are not the subjects we usually photograph. In the real world all the Pentax lenses can be used with confidence.

Forgive me if in saying that I came across as being smart, but I read these reviews on Photozone and the mtf figures are what I judge a lens by.
I never read the barrel distortion and vignetting figures. Today however I was about to buy a Pentax 18 - 250 of a forum member but changed my mind after reading the full review,and seeing the barrel distortion and vignetting figures, was I wrong ?
I shoot landscape, mostly at wide angel but often see wildlife which is why I want a wideangle with a long reach. I missed a superb shot of a heron the other day because I only had a Sigma 17 - 70 on.

The Sigma 18 - 125 caught my eye when I saw it for sale at SRS but the 18 - 250 would cost the same, what would you do ?
I highly respect your posts on here by the way

You can't fairly compare the MTF figures on Photozone.de of a Canon-fit lens to a Pentax-fit lens because the cameras used are different, but you can see how they compare to other Canon-fit lenses and Photozone's "excellent" threshold.

So I reckon the review is somewhat useful. The optics are bound to be same with the Canon and Pentax fit versions.

Distortion and vignetting can be corrected to some extent in post processing. The Pentax/Tamron 18-250 is commonly thought to be the best superzoom in general, so you should seriously consider it if you do want any superzoom.

Testing lenses is a very complex affair, as is interpreting the test results. There's a good deal more to a lens than resolution alone, or indeed than figures for distortion and vignetting. You will never get a perfect lens and one that appeared to be nearly perfect when photographing test charts might not be so good "in the field" for a variety of reasons. Apart from anything else, the distance the tests were carried out at will also be relevant factors and you can be sure only the manufacturer will have gone to the required lengths with this.

You don't come across badly in any way, so don't worry about that. Technical conversations get technical, there's no avoiding it.

I have not done bench tests on the 18-250mm Pentax lens that Sue uses, but I do know that she takes brilliantly sharp images with it and I have been very impressed. Its resistance to flare is excellent - the other night at Plover Scar I noticed you can see right through the lens and the individual elements are quite invisible, a good sign of high efficiency coating. Her images in normal use do not show vignetting. Sharpness and resolution are fine.

In summary I would say if you had gone with your "gut feeling" and ignored the tests you would have been very happy with the lens. What more is needed?

Many thanks John for such an informative reply. Can I ask what you think of the Sigma 18 - 125 that is the subject of this thread ?, do you think it will be as good as the 17 - 70 ?,if so it would be a serious contender for my next lens with that kind of reach.
SRS only got them yesterday and have not had time to test but kindly have offered to take it back if I am not happy, but surely if it was "optically flawed" it would show up in the photozone review.