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04-25-2019, 07:16 PM   #1
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How do Pentax lenses for a K-70 compare with those of other companies?

Hi, I'm pretty happy with my K-70 but I have trouble getting really tack sharp focus. I'm wondering what the reputation of Pentax lenses is as compared with other companies' lenses that fit the K-70. Or would I have better results if I stepped up to another Pentax model and used my Pentax lenses. I have the 55-300, 18-135, the 40 prime and the 100 macro. Thanks.

04-25-2019, 07:20 PM   #2
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perhaps some examples of your shots that you aren't happy with; we could take a look and maybe help with a solution?
04-25-2019, 07:26 PM - 1 Like   #3
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These tips are good, general information, that you might consider:

17 Tips for Taking Tack Sharp Photos | Photography Mad
04-25-2019, 08:54 PM   #4
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To answer your question, first party lenses (within a comparable class) are generally superior in terms of both optics and features such as build quality and AF speed. However, as others have already mentioned, there are many factors which could be affecting sharpness. There could even be something wrong with the camera.


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04-25-2019, 09:09 PM - 1 Like   #5
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QuoteOriginally posted by Joyce Keay Quote
Hi, I'm pretty happy with my K-70 but I have trouble getting really tack sharp focus. I'm wondering what the reputation of Pentax lenses is as compared with other companies' lenses that fit the K-70. Or would I have better results if I stepped up to another Pentax model and used my Pentax lenses. I have the 55-300, 18-135, the 40 prime and the 100 macro. Thanks.
You'll see on this forum plenty of pictures taken with those lenses, Joyce, so we need to figure out what's going on.

Could you post examples with their EXIF data intact? We can look at them and try to diagnose.
04-26-2019, 01:40 AM   #6
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QuoteOriginally posted by Adam Quote
To answer your question, first party lenses (within a comparable class) are generally superior in terms of both optics and features such as build quality and AF speed. However, as others have already mentioned, there are many factors which could be affecting sharpness. There could even be something wrong with the camera.
Dunno, sigma 30 1.4 is optically better than 1st party options of comparable fl. Af sucks for that lens tho...
And i found both sigma 17 50 2.8 and tamron 17-50 2.8 better than 1st party options for all dslr manufacturers. Only their build quality somewhat lacks but they are ok for most of the tasks...
04-26-2019, 05:11 AM - 1 Like   #7
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You list "100 macro" - I assume you have a new series DFA 100/2.8 reviewed here?

Pentax-D FA 100mm F2.8 WR Macro Review - Introduction | PentaxForums.com Reviews

Put the other lenses aside (not that there is anything wrong with them), and see what you can do with this lens. It is capable of producing very sharp images. You should have no issues with this on your K-70. If you can't get sharp images with this lens on the K-70, then you need to start investigating what is wrong, be it technique (most likely) or something else. Sample images always help.
04-26-2019, 05:54 AM   #8
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The lenses you have are as good as any other comparable lenses. That said, it also depends on your expectations and what you mean by "tack sharp". For example, the 55-300 is good for a budget telephoto zoom, but you should not expect it to perform like a high-end zoom costing thousands of $ or a telephoto prime lens costing as much or more...

So, as others said, some pictures with the exif data would help. More often than not, it turns out the issue is the technique, not the gear. It's somewhat like cooking, if the recipe isn't good in the first place it doesn't really matter which brands of ingredients, cookware or oven are used...

04-26-2019, 06:56 AM   #9
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QuoteOriginally posted by Trickortreat Quote
Dunno, sigma 30 1.4 is optically better than 1st party options of comparable fl. Af sucks for that lens tho...
And i found both sigma 17 50 2.8 and tamron 17-50 2.8 better than 1st party options for all dslr manufacturers. Only their build quality somewhat lacks but they are ok for most of the tasks...
The comparison on this website showed the 31 ltd was better at a given ƒ-stop, the 30 1.4 was better (creamier bokeh) at 1.4 than the 31 was at 1.8, but that was it. Not only was that the testers opinion but he posted comparison photos so we could make up your own minds. To me the difference were clear, and the 30 1.4 was really only better in price. (unless you really shoot in manner where 30 1.4 is a thing.)

With the Tamron 17-50 there are numerous reports of de-centering, which mine suffers form as well. You can't use it for landscapes even at ƒ8. With older lenses like the 17-50, you don't get water residence and the build quality isn't as good. So in our experience better out of the box, but 5 years later, not better. I simply refuse to compare WR lenses with no WR lenses. Those water seals make the lenses smooth in away non-WR lenses doesn't seem to match.

Personally, after starting off on a 3rd party lens shopping spree to keep costs down, almost everything I used to carry has been replaced by Pentax glass.

The 3rd party lenses still in use are the Tamron 90, which my wife loves, but I've picked up a DFA 100 macro for my own use, The Sigma 8-16, Pentax doesn't make a similar lens, and my Sigma 70 macro which has been used infrequently since I got the DFA 100 macro, and my Tamron 300 2.8. Look at the reviews you can see all those lenses get stellar reviews. But they are all in focal lengths Pentax doesn't make, which is how I've always seen 3rd party lenses. They have to fill holes in the Pentax line-up.

You could do a whole 3rd party lens thing and not buy any Pentax glass, but this point of my 22 lenses, only 4 aren't Pentax and those 3rd party lenses get used a fraction of what my Pentax lenses do.

Last edited by normhead; 04-26-2019 at 07:06 AM.
04-26-2019, 07:08 AM   #10
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QuoteOriginally posted by normhead Quote
With the Tamron 17-50 there are numerous reports of de-centering, which mine suffers form as well. You can't use it for landscapes even at 8. With older lenses like the 17-50, you don't get water residence and the build quality isn't as good. So in our experience better out of the box, but 5 years later, not better. I simply refuse to compare WR lenses with no WR lenses. Those water seals make the lenses smooth in away non-WR lenses doesn't seem to match.

Personally, after starting off on a 3rd party lens shopping spree to keep costs down, almost everything I used to carry has been replaced by Pentax glass.
My experience has been the same with the Tamron. And I will add that many if not most copies are plagued with AF issues (in Canon and Nikon mounts as well). But I got it for cheap, that's for sure. But I also got nothing more than I paid for... I also had an underwhelming experience with Sigma. I even sent the lens for repair but got it back in the same condition with a mention that the lens was within specifications, which seem to be quite permissive.

So, like you, they were replaced by Pentax lenses and I never looked back...
04-26-2019, 07:23 AM   #11
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QuoteOriginally posted by CarlJF Quote
I also had an underwhelming experience with Sigma. I even sent the lens for repair but got it back in the same condition with a mention that the lens was within specifications, which seem to be quite permissive.
I forgot my Sigma 18-250, which we wanted as a one lens solution for hiking and canoe trips. It was repaired under warranty after failing 3 years in, and it was noted that it was de-centered. They couldn't fix the de-centering. It's now a good portrait/action lens for my daughter-in-law's dog images. But as a landscape lens it failed horribly. And it wasn't nearly as sharp as my 55-300 PLM.
04-26-2019, 09:09 AM   #12
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QuoteOriginally posted by normhead Quote
The comparison on this website showed the 31 ltd was better at a given -stop, the 30 1.4 was better (creamier bokeh) at 1.4 than the 31 was at 1.8, but that was it. Not only was that the testers opinion but he posted comparison photos so we could make up your own minds. To me the difference were clear, and the 30 1.4 was really only better in price. (unless you really shoot in manner where 30 1.4 is a thing.)

With the Tamron 17-50 there are numerous reports of de-centering, which mine suffers form as well. You can't use it for landscapes even at 8.
Dunno about the 31 ltd and 30 sigma comparison. Never had it but after searching some independent test results and sample photos i really dont see 31 ltd having advantage at any fl. Both seem pretty much the same except sigma is faster.
Abot tamron on the other hand - that lens is excellent. Had no centering issues. Shooting at has problems? Where did you get that idea? Any samples? I had no issues at that f number (or any for that mater) at all. Lets remember that pentax 16-50 had a fair share of issues of its own... wether is that centering or mechanical issues and optically is behind the Tamron by a fair margin.
Lets not forget that Tamron is a parfocal lens and none of the 1st party options (Nikon/Pentax/Canon) are.
04-26-2019, 09:16 AM   #13
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QuoteOriginally posted by Trickortreat Quote
Dunno about the 31 ltd and 30 sigma comparison. Never had it but after searching some independent test results and sample photos i really dont see 31 ltd having advantage at any fl. Both seem pretty much the same except sigma is faster.
Read up.
FA31 VS Sigma 30 1.4 Art - PentaxForums.com

At the time of this his test Digitalis still had his testing bench up and running, so he did his own analysis.
The relevant quote
QuoteQuote:
the FA31 limited is sharper in the corners at f/1.8 than the sigma 30mm f/1.4 is at f/11.
04-26-2019, 09:32 AM   #14
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QuoteOriginally posted by normhead Quote
Read up.
FA31 VS Sigma 30 1.4 Art - PentaxForums.com

At the time of this his test Digitalis still had his testing bench up and running, so he did his own analysis.
The relevant quote
No its not, Sigma is better in all optical benchmarks till about f2.5 by a hefty margin

Sigma A 30 mm f/1.4 DC HSM review - Image resolution - LensTip.com
Pentax smc FA 31 mm f/1.8 AL review - Image resolution - LensTip.com

after that 31 ltd pulls slightly ahead. 31ltd never resolves its coma issue while sigma fares really good at it, so no astro stiching for 31ltd while sigma is probably the best crop lens for it.
04-26-2019, 09:52 AM   #15
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QuoteOriginally posted by Trickortreat Quote
No its not, Sigma is better in all optical benchmarks till about f2.5 by a hefty margin

Sigma A 30 mm f/1.4 DC HSM review - Image resolution - LensTip.com
Pentax smc FA 31 mm f/1.8 AL review - Image resolution - LensTip.com

after that 31 ltd pulls slightly ahead. 31ltd never resolves its coma issue while sigma fares really good at it, so no astro stiching for 31ltd while sigma is probably the best crop lens for it.
There should be warning on all sites of this type that you can't compare lenses on different systems. These comparisons are useless. One done on a Canon, one done a Pentax with different sensor characteristics.

So why is Digitalis' comparison better? Both lenses and comparison images were done on the same sensor. Every site from DxO to Optical limits will tell you not to compare lenses using different camera bodies.

You also made the mistake of using ancient cameras for the comparison. If memory serves me well, 2013 was the big year for those models.

Digitalis said the 31 1.8 was better from 1.8 on, and 2.4 isn't that different, you're arguing well within lens sample variation. For 90% of it's range the 31 is better. And since for most of us 31 is a landscape lens we can easily argue that for most use the 31 is better. But if you want to argue the 30 is better for a niche market like astrophotography, I'll defer to your experience, if you have actual experience, not just chart numbers.

I can't tell you how many times someone has posted images proving this that or the other lens was bette than the 31, and how many times we had to point out why the 31 was better.

But the relevance of stating so emphatically that the 30 is better is seriously diminished by the caveat "for astro-photography." and even by your own accounts, at less than ƒ2.4. That's a pretty limited range. It's not often a lens is better than another lens at everything. All that matters is that it's better at what you use it for.

In a general statement like the above, the caveats need to be explained.

Last edited by normhead; 04-26-2019 at 11:09 AM.
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