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07-20-2015, 02:50 AM   #1
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What is the sharpest lens for a K3, 17-70 or similar?

I have been using the Pentax DA 17-70mm f/4 SDM for a few years.

Most of my shooting is done in TAV mode, and I find the 17-70 covering nearly all requirements. The only other lens I have is a (something like 50-200) dirt cheap Pentax one which gets used once a year. (A lot has changed since carrying an OM2SP, later OM4Ti, 5 lenses and 25 rolls of Kodachrome 25 and I am not sorry).

It works great, of course, but sometimes cannot focus properly. Also I *feel* that the K3 should be a lot sharper than I am getting. Mostly I shoot at F8 which according to reviews is optimal for most of these lenses.

I may be missing something but the only other *Pentax* option is a very similar WR lens. Not worth changing for that one!

What is the very best quality lens in the 17-70 sort of range, regardless of price, which will fully work with the K3?

07-20-2015, 03:22 AM   #2
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In my experience, Sigma 35mm is exceptionally sharp. 70mm Ltd too. Both awesome lenses

21mm Ltd is great lens too. Not the sharpest lens around, but a really good performer. Was my most used lens before I got the Sigma 35mm.

Last edited by Apapukas; 07-20-2015 at 03:27 AM.
07-20-2015, 03:22 AM   #3
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hi Peterh337

i have the 18-135 WR lens which is 99.9% of my shots spot on. I believe the new pentax lens HD PENTAX-DA 16-85 should be a better choice from though i havent used it.
My sharpest lens was my Sigma 18-35 1.8, but since half of the shots where not focused correctly (even with the Sigma dock for adjustment ) i sold it.

But since almost 2 years i use only primes for the known advantages. My favorite: DA 15mm limited for landscape.
cheers,david
07-20-2015, 03:37 AM - 1 Like   #4
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QuoteOriginally posted by peterh337 Quote
Also I *feel* that the K3 should be a lot sharper than I am getting. Mostly I shoot at F8 which according to reviews is optimal for most of these lenses.
The K-3 is as sharp as it gets, the problem are the lenses. If you put a soft lens on there, you can have the highest resolution camera on the planet and it won't help. This is why it is generally a good idea to invest more in lenses than in the camera. So people buy the K-50 or K-5IIs (getting really affordable these days) and great lenses, instead of K-3II with kit lenses. The kit lenses are not the worst (other brands had some really bad kit lenses), but they are far from the best. Using them at f8 is a good start, but you need good technique overall.

The 17-70mm is not a bad lens, but its not the best out there, either. Do you want just a super sharp lens? Then get something like DFA 50mm macro or Sigma 70mm macro. These will give you the most absolute sharpness. Zoom lenses are already a compromise and won't be as sharp. The question is, what is adequate? What are your priorities, a comfortable zoom range or sharpness at all apertures?
Sigma has some good zoom lenses, and Tamron has some good, but more affordable lenses:
DA* 16-50mm vs. Sigma and Tamron 17-50mm F2.8 Comparison Review - Introduction | PentaxForums.com Reviews

Sigma 17-70mm F2.8-4 Contemporary Review - Introduction | PentaxForums.com Reviews

But you might want to look into getting at least a DA 35mm or DA 50mm. These are the "low-tier" of Pentax primes, affordable, but really they have great image quality. In terms of sharpness and image quality they beat many older or third-party primes and most zoom lenses. I think they are best bang for buck



Last edited by Na Horuk; 07-20-2015 at 03:48 AM.
07-20-2015, 04:16 AM   #5
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QuoteOriginally posted by peterh337 Quote
I have been using the Pentax DA 17-70mm f/4 SDM for a few years.

Most of my shooting is done in TAV mode, and I find the 17-70 covering nearly all requirements. The only other lens I have is a (something like 50-200) dirt cheap Pentax one which gets used once a year. (A lot has changed since carrying an OM2SP, later OM4Ti, 5 lenses and 25 rolls of Kodachrome 25 and I am not sorry).

It works great, of course, but sometimes cannot focus properly. Also I *feel* that the K3 should be a lot sharper than I am getting. Mostly I shoot at F8 which according to reviews is optimal for most of these lenses.

I may be missing something but the only other *Pentax* option is a very similar WR lens. Not worth changing for that one!

What is the very best quality lens in the 17-70 sort of range, regardless of price, which will fully work with the K3?
A couple of questions that will help people give you the best answers:

1) Are you looking for a zoom lens or a prime which will usually be sharper than any zoom?
2) Did you try to micro-adjust the focus on the DA 17-70? (for a zoom, I find it quite sharp with excellent contrast)
07-20-2015, 04:23 AM   #6
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Many thanks all...

I am going to look at the Pentax DA 16-85mm F3.5-5.6ED DC WR. It is hard to find here in the UK currently. At the price (GBP 500 at parkcameras.co.uk) it should be very good

I wonder whether I should wait for this lens to be out for a bit though. The SDM motor had a near-100% failure rate and my 17-70 had to go back, about 2 weeks before my 3 year warranty expired

Unfortunately I can't really use prime lenses. Most of my stuff cannot be set up with plenty of time. Also quite a lot is done out of a light aircraft (yes, trying to get quality there is a bit impossible) and I just find the zoom to be massively useful there and elsewhere too. Even when doing "landscape" stuff, I don't want to change lenses. My back isn't good enough anymore for carrying several lenses in a bag. Yesterday I met a bird watcher who carried two Canon 7s, with different lenses, and many years ago I knew one who carried two Hasselblads for the same reason! I don't want to do that either.

I did once try to micro adjust the focus. I found a chart on the web which you print out and on which you can see very fine lines. In that test, the lens seemed to be optimally set up.
07-20-2015, 04:33 AM   #7
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Dc motor is totally different to sdm motor - I wouldn't be concerned about its reliability. Sdm is a 'regular' small motor with a little rack and pinion, dc is a 'ring' motor which means much more torque and no flimsy bits to fall apart.
07-20-2015, 05:38 AM   #8
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I had the 17-70 for a while that served me well, I also bought the Tamron 17-50. The Tamron 17-50 is cheap and noticeably sharper with the K-3, from f4, from 17 to 50, no restriction. Since then I sold the 17-70. The Tamron 17-50 is cheaper, but if it were now, I'd probably get the 16-85 or 20-40 rather than the Tamron 17-50, because of silence AF and color rendition. If I was on a budget, I'd still buy the Tamron 17-50 a second time, or the Sigma 17-70 C.

07-20-2015, 06:24 AM   #9
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If you open yourself up to primes and a few more mm of focal range then the FA 77mm will probably reign supreme. Any of Pentax's other primes won't be far behind. They are all ridiculously sharp.
07-20-2015, 06:38 AM   #10
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I have bought the 16-85 on Amazon.co.uk just now

The 17-70 will go on Ebay the same day (a rule we have in the house ).
07-20-2015, 06:43 AM   #11
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The Sigma 18-35 Art is crazy sharp - but... It took me two copies to get a good one for AF, and others report never getting one. If you're willing to take the chance, when this lens gets it right it's second to none!
07-20-2015, 06:48 AM   #12
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If you should Jpeg you can boost the sharpening by a couple of notches in-camera...
07-20-2015, 06:51 AM   #13
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Although I don't have the 16-85, but I think it would be better and sharper than the 17-70. OTOH, I have the 20-40, it is quite sharp and less weight.
07-20-2015, 07:03 AM   #14
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If I want the best result, I use DNG (I shoot jpeg to one SD card and DNG to the other, always) and then convert to 95% quality jpeg in Lightroom, and keep the jpegs which are around 15MB. I would not keep DNG because it isn't future-proof; the format keeps changing in subtle ways.

Historically, generally, in-camera jpeg compression was not as good as the expensive PC apps (especially on things like foliage) and while it is in LR one can do the usual adjustments all in one go.

I do just cropping and simple haze removal, and on any pics where the ISO ended up (I nearly always use TAV mode) over about 500 one can see visible noise so I de-noise the luminance channel, and that's it.
07-20-2015, 07:32 AM   #15
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Are you comparing images from your older camera and your K-3 on-screen? You should try comparing prints.

When I first started shooting with a K-3, it seemed to me like my images were less sharp than those taken with a 16 MP camera. But the prints look as good or better.

I don't know enough about the science of photography, but this older blog post suggests a reason why your higher resolution image might look softer on-screen.
Why Your 21MP File “Looks Softer” Than Your 12MP File at 100% MagnificationG Dan Mitchell Photography
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