I'm currently loaning a Tamron 1.4x PZ AF MC4 & autofocus works perfectly on my GX10 (K10D) with the new DA 55-300...could it be anything to do with firmware perhaps? Sorry I can't be more help !!

simon

I upgraded the kit using the Sigma 17-70 & it's a significant upgrade - I noticed a big difference, initial indications are that the Sigma is pretty much a match for the new Pentax 17-70, although it's still early days with the pentax.

I've also just bought the 10-20 & it's taken me 3 copies to find a good one, it seems to suffer sample variation more than most - essential to test it out if you do buy one..

Trying to answer your question exactly though is a bit difficult because it very much depends on your photography...the 17-70 is a very good "walkabout" focal range whereas the 10-20 is much more limited.

Sorry to not be more helpful but your priorities may differ from others

simon

Thanks for the feedback everyone, best thing for me to do is give it a try

simon

Having hopefully just recieved a good copy of the Sigma 10-20 I'm considering polariser options, one is pretty much permanently on my Siggma 17-70...

the problem with wide angle lenses is I believe that polarisers can create uneven polarisation effects but to current owners just how bad are these "effects" ?

I normally go with Hoya Pro 1 D filters but a 77mm one is very expensive, is there a similiar quality viable alternative ?

Any advice much appreciated

simon

Well, just recieved the 3rd copy & it looks like I might be able to produce some shots to the standard of those posted...this one looks to be a keeper on 1st impressions...

Certainly doesn't suffer significant de-centering or lack of sharpness, distortion levels also seem less than on the previous 2 copies. Intend to post my 1st landscape shots once this weather gives me a chance !!

simon

Fair enough...not one to dwell on a single review either but thought it might be useful... there's quite a few users other than me on here who have also been very pleased with the lens

simon

Just came across this whilst browsing the www...a mini-review of the new DA 55-300 by popphoto.

The sharpness results back-up what many of us current 55-300 owners know..it's pretty impressive !!

http://www.popphoto.com/cameralenses/5469/pentax-da-55-300mm-f4-58.html

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If cash is a consideration and you are considering the 17-70 range the Sigma 17-70 will serve you well

simon

Can't comment on the 2x but just recieved a Tamron 1.4x PZ MC4 to try out with my new DA 55-300, generously loaned to me by a fellow Pentaxian...intend to try it out over the next week or two & will post my findings

simon

It's certainly true that lens manufacturers don't seem to meet the same high levels of product quality we have become used to in other electronic products...as mentioned perhaps they do rely on the fact that some buyers may not be aware of the fact that poor quality shots are the result of a defective lens & not their own photographic skills...looking around the WWW the Sigma 10-20 certainly seems to be one of the worst culprits though, many problems & it seems Sigma are not doing much to improve the situation.

From Sigmas point of view & considering the current/future economic climate it does seem a little bit suicidal to allow this situation to continue. If my next 10-20 is a lso a poor copy they've definitely lost a potential customer, I won't consider a Sigma again !!

simon