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Forum: Pentax SLR Lens Discussion 02-04-2013, 06:24 PM  
constant aperature or focal length?
Posted By kevinf7
Replies: 29
Views: 1,559
I agree get the 17-50. Personally I prefer better IQ over the extra 20mm at the long end.
Forum: Pentax SLR Lens Discussion 01-02-2013, 05:02 PM  
Is the Sigma 17-50mm f/2.8 much better than the Pentax DA 16-45mm f/4 ?
Posted By kevinf7
Replies: 9
Views: 2,144
I am not sure about the Pentax 16-45 but I used to own the Pentax 17-70 f4 so I can compare the Sigma to this. The Sigma 17-50 f2.8 is my current walk around lens. The Sigma is very sharp wide open at 2.8 and extremely sharp stopped down a little. It easily beats the Pentax 17-70 which was soft wide open. The main advantages of the Pentax is build (bit better than Sigma) and colour rendition (Sigma is a touch cooler). Overall I am very happy with the Sigma. Most of my shots are wide open or near wide open so the sharpness really makes a difference to my photos.

Also I never noticed any problems with soft corners with the Sigma as reported.
Forum: Pentax SLR Lens Discussion 01-23-2012, 10:00 PM  
DA* 16-50: Is it worth it?
Posted By kevinf7
Replies: 30
Views: 6,781
I read about the softness of the 16-50 at f2.8 too which is why I bought the Sigma 17-50 f2.8 instead. The Sigma is cheaper than the Pentax although it doesn't have weather sealing. With the Sigma I am absolutely blown away by its sharpness and IQ at 2.8. I also have the 50-135 and if you think that lens is good the Sigma is even sharper! I used to own the Pentax 17-70 f4 as well. My conclusion is that Pentax zooms in general are indeed quite soft wide open. I even consider the 50-135 a little soft wide open when compared to the Sigma.
Forum: Pentax SLR Lens Discussion 10-31-2011, 10:06 PM  
sigma 17-70 vs Tamron 17-50 vs Pentax 17-70
Posted By kevinf7
Replies: 19
Views: 31,927
I had both the Pentax 17-70 and Sigma 17-50 and I can say that the Sigma is much sharper than the Pentax. It is tack sharp by f3.5 and extremenly good at f2.8. Have never used the Tamron 17-50 nor Sigma 17-70 so can't comment on them.

Some other differences between the Sigma and Pentax:

- Pentax autofocus is a little bit quicker but Sigma is good enough
- Autofocus on both Pentax and Sigma are silent
- Pentax has a weather seal on the mount which is nice.
- Sigma is a bit heavier and bulkier but ok for me.
- Colour rendition is good for both lenses (at least to my eyes)
- Sigma for some reason overexposes slightly but that is easily corrected by the camera.

I returned the Pentax and kept the Sigma. I find that I do miss the 50-70 occassionally especially for portraits but I guess you can't have everything!

BTW I found the f2.8 really useful despite the low light capabilities of the K5. It is great for shallow DOF pictures. The problem with the Pentax was that it wasn't sharp enough at f4 (at least to me) and you often had to stop down to f5.6 or more for decent IQ but that meant you couldnt get any good DOF pictures...
Forum: Pentax SLR Lens Discussion 10-31-2011, 09:46 PM  
Expecting too much from my Sigma 17-50mm?
Posted By kevinf7
Replies: 23
Views: 2,282
Mine is very sharp at f2.8 and tack sharp already at f3.5. This is a really sharp lens. I suggest tuning the camera to fix front/back focus problems.
Forum: Pentax News and Rumors 10-25-2011, 10:23 PM  
17-70/4 review, what the .. ?
Posted By kevinf7
Replies: 31
Views: 17,297
Just an update to this thread which I stumbled upon in Google. Regarding the review: Pentax DA 17-70mm f/4 SDM Lens Review

I found my copy which I received a few weeks ago (Oct 2011) behaving exactly like how it was described in the review. It was soft wide open and not particularly sharp especially at the longer focal lengths (50-70). It was better only at the wider angles and when stopped down a bit. Overall I was not satisfied with the sharpness and have since returned the lens.

I dont know if my copy was a bad one (maybe not given the above article). Out of curiosity do any other 17-70 owners also experience the same IQ results as those shown in the article?
Forum: Pentax SLR Lens Discussion 10-23-2011, 10:32 PM  
Sigma 17-50mm F2.8 vs Tamron 17-50mm and Pentax DA* 16-50mm
Posted By kevinf7
Replies: 89
Views: 25,133
I just got my Pentax 17-70 a few days ago to complement my K5. I have to say that I am slightly dissapointed with it wide open (f4) as it is quite soft. I've cranked up the sharpness setting to max on my K5 and it improves slightly. I've also fine tuned the micro autofocus adjustment so the reason isn't that.

All in all, a good lens. Just not as sharp as I would like at f4. Having said that I've read reviews of the Sigma 17-70 and it seems to perform similarly to the Pentax so I wouldn't necessarily go for it over the Pentax.
Forum: Pentax SLR Lens Discussion 10-23-2011, 04:20 AM  
Anyone compare the 'walkaround' Pentax zoom lens? DA*16-50 & DA17-70
Posted By kevinf7
Replies: 11
Views: 1,905
I just got my new 17-70 and I must say I am slightly disappointed with it wide open. Compared to my old Olympus 14-54 f2.8-3.5 it is no where as sharp at all focal lengths when wide open - that is f2.8-3.5 Olympus vs f4 Pentax. You really need to stop it down to f5.6 or 6.5 before reaching the IQ levels of the Olympus. I've only had it for a couple of days so its early days yet, but that's my findings so far. I think to reach really good IQ levels you really need to go for primes such as a DA 40 or DA 70 (my next 2 lenses!)

Having said that everything else about the lens is really good - the size, weight, focal distance, build, zoom speed and noise (lack of), etc.
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