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12-05-2015, 05:48 PM   #1
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Sigma 17-50 2.8 with K5

Just bought from B&H my Sigma 17-50 for my K5. Been doing quite a few test shots and here's some thoughts on it.

Its not that great in low light...my cheap Pentax 50 1.8 seems better.
Seems sharp, but not totally sure on that at f9 and beyond. Nothing seems that "great" when looking and pixel peeping.
Overall, kinda underwhelmed. Not as sharp as I was hoping...or really that different than Kit lens.
Super quiet..crazy quiet which is awesome.
Fairly heavy, wish it was a little bit further reach.

Thinking maybe the HD PENTAX DA 16-85mm f/3.5-5.6 ED DC WR Lens would be a better fit? Better range for only 100 dollars more?? Granted indoors that might not be the best, but I shoot mostly outside and the 50 I have does the trick indoors for now...

Are there settings or general rules of thumb with this lens in particular that I should be aware of with my camera body? Conditions haven't been that great yet to really put it to the test. I am considering returning it unless I can get some better results.

Some say, the Tamaron is a better deal, and lens..thoughts?

Totally willing to admit, it could be the user that is having the issue ...not the lens or the camera.


Thanks!


Last edited by tpentax; 12-05-2015 at 07:52 PM.
12-06-2015, 05:24 AM   #2
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The SIgma 17-50mm is the sharpest zoom that DPR has tested for K-mount. They have not tested the Tamron 17-50 on a Pentax camera, but they did test it on a Nikon D7000. The K-5 and D7000 use the same 16mp Sony sensor, therefore results are directly comparable. Click on the Measurements tab, then on Sharpness and Field Map. Compare by focal length and aperture. Green is good, red is poor.

Tamron SP AF 17-50mm F/2.8 XR Di II LD Aspherical [IF] Nikon on Nikon D7000 vs Sigma 17-50mm F2.8 EX DC HSM Pentax on Pentax K-5

Every review site I was able to find that reviewed both reported the same results; the Sigma is noticeably sharper at wide apertures. The Sigma's superior build quality and silent auto-focus sealed the deal for me. It is annoying that the focus and zoom turn the wrong way, but in every other way I love this lens. I used mine with a K-3 for landscapes on Saturday, a dinner party Saturday night, and a kid's birthday party Sunday afternoon. It performed flawlessly.

I suspect you may be having trouble with focus accuracy. The K-5 is known for poor auto-focus in tungsten light, and only has f/5-6-sensitive focus points, therefore AF is not as accurate with a fast lens as the K-5 II or K-3. To ensure the best results, you should calibrate the lens to your body using AF Adjust.

My research indicates the Tamron 17-50 has a reputation for focus issues across all brands, not just Pentax. The AF issue sometimes cannot be addressed with AF Adjust, because calibration varies depending on focal length. The Tamron 17-50 is a great lens if you get a good one, but the Sigma is better.

IMO you chose the right lens, you just need to make sure it is working properly.
12-06-2015, 11:15 AM   #3
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I have a K5IIs and have the tamron 17-50 2.8 and I think is sharp. Would have bought sigma but needed lens fast, happy with what I have, may have got lucky.

That Pentax 50 1.8 is a very sharp lens, some of my better images really. I did have a problem tamron 28-75 2.8 images not sharp, that was a back focusing problems.

Maybe see if it is forward or back focusing, My version is ok in low light. From what I've read Sigma 17-50 should be super sharp.

Good luck!

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12-06-2015, 09:32 PM   #4
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Thanks for the comments! Is it hard to do the AF Adjust? haven't dabbled in that before. Yea, I am tempted to sell the K5 and get the K3ii. This will serve as my back up body(eventually)...if, and its a big IF the FF ever gets released. Really like the 50 1.8..so cheap but its yielded some great results. Will upload a shot tomorrow...

12-06-2015, 11:46 PM   #5
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QuoteOriginally posted by tpentax Quote
Thanks for the comments! Is it hard to do the AF Adjust? haven't dabbled in that before. Yea, I am tempted to sell the K5 and get the K3ii. This will serve as my back up body(eventually)...if, and its a big IF the FF ever gets released. Really like the 50 1.8..so cheap but its yielded some great results. Will upload a shot tomorrow...
It is a lot easier to make a good prime, than a good zoom. Zooms are usually worse than the primes, even if they are good zooms. If something is difficult to make and requires a lot of material, then it's likely to be more expensive.

In any case, your problem is almost definitely AF microadjustment. I am not sure if your K-5 has microadjustment in the menu. If it doesn't you will have to send the camera and the lens to sigma for a calibration. The pro is, that once you do it, it will probably work very well. I don't think they charge for it either.
12-07-2015, 12:03 AM   #6
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I have that lens, Tpentax, and it's great. You better get out your tripod and make the micro adjustments.

I did the same to get my Sigma 35mm Art very sharp on my K-S1.

Last edited by clackers; 12-07-2015 at 12:52 AM.
12-07-2015, 04:57 AM   #7
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QuoteOriginally posted by rrstuff Quote
It is a lot easier to make a good prime, than a good zoom. Zooms are usually worse than the primes, even if they are good zooms. If something is difficult to make and requires a lot of material, then it's likely to be more expensive.
The 50mm f1.8 has a faster aperture, smaller size and lower CA, but the Sigma 17-50mm is slightly sharper at 50mm, from f2.8 through f8. That is very impressive for a zoom.

Sigma 17-50mm F2.8 EX DC HSM Pentax on Pentax K-3 vs Pentax smc DA 50mm f1.8 on Pentax K-3

QuoteOriginally posted by rrstuff Quote
In any case, your problem is almost definitely AF microadjustment. I am not sure if your K-5 has microadjustment in the menu.
It has. All of the upper tier Pentax bodies from the K20D on have AF Adjust.
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