tammy 17-50 vs sigma 17-70 OS HSM vs 18-135mm

Hello,

I own a tammy 17-50mm f2.8 which I am very happy with in terms of quality. I however realised this wkd that 50mm is too short for me! Although I own a 18-250mm which I find really good when travelling, I dont think we can compare the quality of the two. Therefore it leaves me unsatisfied (!). I was tempted to try the 28-75mm ultimate wedding lens, but think I would miss the 17-28mm range too much.


I havent seen that many reviews of the 17-70mm OS version, it seems the OS is not any better than the Pentax body IS, is it true?

How does it compare to the pentax version? is it overall better or similar? the pentax seems to be weak on the focusing from 50mm onwards - so not very appealing. However the pentax has 67mm filter size so I could use my filters (vs 72mm for sigma).

Then comes the pentax 18-135 which sounds like my dream lens, but much more expensive for now, would need to be in the £300ish range.. or should i just wait a few months? and/or buy it second hand?

thanks

I have the OS-version of the Sigma 17-70 and here the OS really works. Not every Sigma lens with OS built-in has the advantage over the SR of the camera itself but I have done some tests and could win 4 stops easily. I have a steady hand though and can win 3 stops and maybe 4 with SR on also, but with the Sigma I think I can push it above 4 stops without too much problems. Won't even think about it when I use SR.

I know this is not a scientific test but reviews also mention the 4 stop gain when using the OS on this lens.

I think the Tamron will edge out the 17-70mm when it comes to IQ but like you said you have more range.

At 70mm subject movement is likely to be a bigger problem than camera movement. I would have thought that it would have been impossible to notice any difference between camera SR and lens SR at 70mm
Apart from noticing the price difference that is

Lots of wedding togs used to hold 6x6 cameras steady with 100ISO film by candlelight

4 stops seems crazy! i know that's what sigma claims but i am sceptical here!
thanks though it's good to know -

I've got no experience with the Pentax mount but I know some people with the Sony 17-70 OS weren't too delighted with it they were under the impression that the Image Quality wasn't as good as the older non OS one, I've only ever had the non OS one and was happy with it was a good lens, but your right its that or the Tammy really!

I have the non OS Sigma 17-70mm 2.8-4.5 and the IQ is stunning for it's class. It's only marginally behind my DA* 50-135 and frankly because of this I have little interest in getting a DA* 16-50 now.

Maybe I just have an exceptional copy.

everyone has the non OS version though... i like the OS one also for the hsm, and the third stop at 70mm... although 1/3 stop is not that much actually - let me reconsider my comment! now cant remember why else i wanted the OS version, well i guess if it is better than the SR then it might make sense as could shoot at f4 with less light.

still not convinced by the sigma but i do want something longer than 50mm!