DA17-70 f4 or sigma 17-70 f2.8-5 or da 16-45 f4 or tamron 16-50mm f2.8?

[lufc2001]

My setup is this.  A K10d with the kit kens 18-55mm, a smc fa50mm1.4, a tamron 28-75 f2.8, and a tamron 28-300 f3.5-6.3.  My most commonly used lens is the tamron 28-75 f2.8 as this is a very sharp lens and outdoor shooting I use the Tamron 28-300 for its versatility and reach. For portraits and bokeh, its the 50mm 1.4.  I am looking at getting a wider angle lens to replace my kit lens which i seldom use. I am looking at the 4 lens mentioned in the title. Obviously for longer reach the 17-70 is better but which is better in terms of performance and sharpness?  All the four lenses (except the DA17-70 f4) is almost the same price in malaysia and the most expensive is the DA 17-70 as it has SDM ) . I have no chance to try any of the lenses. Anyone can help and advice? I am actually looking at replacing all the current lenses i have with just the DA17-70( if your feedbacks are okay ) and the DA 50-135 f2.8. I am also looking at replacing my smcfa 50mm 1.4 with the da 70mm 2.4.  What do you guys think?  and for the longer reaches, maybe i will get the da55-300. REally appreciate your feedbacks especially those who have used the lenses i mentioned above and share the pictures where possible. A million thanks to all.

[Craig]

For a bit more coin you could get the DA* 16-50 2.8 . It is a great companion to the DA* 50-135 2.8.
Plus you will be dust and weather sealed. The IQ and bokeh of said lenses is worth the extra $ in my opinion. I've only used my 50 1.4 and DA 10-17 3.5-4.5 a couple of times since my purchase of the * lenses. Hope this helps with your decision. Happy shooting!

ironshot

[teogin]

If you can manage to find Tamron 17-35/f2.8-4 which is a good lens, close to your 28-75/f2.8 in quality terms, and of course it's a full frame lens, which you can use with older or future full frame bodies.  This lens has stopped being produced and I do not know why, but I am sure that you can find it somewhere.  It deserves your interest for now and future use...!

[calsan]

Not sure if this is a factor or not:  Compatibility with the built in flash?
The built in flash can be obscured by most of the wider lenses - I think not obscuring the flash is probably the design criteria of the kit lens and the reason it's so small (and slow).  The 17-70 will mean you either need to carry flash with you or not use the wider range when using the built in flash.
If you hang onto your kit lens, then you can still have a compact setup for those times when you don't want to carry everything!

I have the Sigma 17-70.
It is very good value for money, and certainly good optically and build wise, even compared with more expensive lenses- however:
Sigma is f4.5 at 70mm - so out performed by the pentax at that end.
I also avoid using the f2.8 except for "emergencies".
Pentax has SDM.  I think this would have swung me in favour of the pentax had it been available when I was making my purchase.
Again, for general use, a fast lens requires more manual control - you don't want the camera automatically using f2.8 all the time.

Pentax 17-70 f4 probably the winner in my opinion, or 16-50 if you have the money and can really justify the need for f2.8

[lufc2001]

If i were to get the da17-70, is there anyway i can get to make it wider by using a converter or filter? if so what are the things i need to achieve this? 

[calsan]

Forgot to add - the sigma's close focusing distance is very good and comes in use all the time.

As far as I know, 16mm is as wide as "normal" zooms get.  For wider than that, you need a 10-20 sigma or a 12-24 pentax.
16 is pretty wide, however.  It's the same as 24mm on a 35mm film camera - about 85 degrees.  That's almost like having eyes on the side of your head.