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04-26-2019, 09:56 AM   #16
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comparisons arent useless, well they are if your agenda is to make them so... They arent 100 directly comparable, no, but sure of hell tell that 31ltd isnt superior to sigma 30.
If you have a better optical mark ill gladly take a look

---------- Post added 04-26-19 at 07:15 PM ----------

QuoteOriginally posted by normhead Quote
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. But the relevance of stating so emphatically that the 30 is better is seriously diminished by the caveat "for astrophotgrapy."
You dont buy a f1.4 lens to keep it above f2.5, for that you could buy the da 35 f2.4. For lenses like Sigma 30 1.4 is the low f numbers that matter the most and in that its a better lens than 31 ltd.

04-26-2019, 10:23 AM   #17
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QuoteOriginally posted by Trickortreat Quote
comparisons arent useless, well they are if your agenda is to make them so... They arent 100 directly comparable, no, but sure of hell tell that 31ltd isnt superior to sigma 30.
If you have a better optical mark ill gladly take a look

---------- Post added 04-26-19 at 07:15 PM ----------



You dont buy a f1.4 lens to keep it above f2.5, for that you could buy the da 35 f2.4. For lenses like Sigma 30 1.4 is the low f numbers that matter the most and in that its a better lens than 31 ltd.
Hardly IMHO. I shot once at 1.4 with an Bowen 85. Once. For a test. Yeah it worked for keeping the eyes in focus. Fortunately both were on the same plane. The hair, the nose, the jawline? Not even.

So when would you personally ever need F1.4 in 30'ish lens to make the Sigma Art 'better"? What would be your circumstance for even wanting to? Yes, there iare folks with peculiar needs that would actually need to shoot at 1.4 (not likely to be the sharpest aperture anyway but) and that's the overriding factor. What would YOU need it for. My FA31 nails focus nearly every time. Consistently and reliably. Does your Art? There's more to a lens than simply a fast F-stop...

Do you know the difference between DoF on a Sigma 30 Art at 1.4 and a Pentax FA31@1.8 from 6 feet? 2 inches, that's it. Pretty much negligible. I'll take the more reliable AF on the FA31 thank you.

Last edited by gatorguy; 04-26-2019 at 12:07 PM.
04-26-2019, 10:31 AM   #18
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QuoteOriginally posted by Trickortreat Quote
comparisons arent useless, well they are if your agenda is to make them so...
If you have a better optical mark ill gladly take a look

---------- Post added 04-26-19 at 07:15 PM ----------



You dont buy a f1.4 lens to keep it above f2.5, for that you could buy the da 35 f2.4. For lenses like Sigma 30 1.4 is the low f numbers that matter the most and in that its a better lens than 31 ltd.
QuoteQuote:
comparisons arent useless, well they are if your agenda is to make them so
Then why does almost every site tell you not to do it?

QuoteQuote:
You dont buy a f1.4 lens to keep it above f2.5, for that you could buy the da 35 f2.4. For lenses like Sigma 30 1.4 is the low f numbers that matter the most and in that its a better lens than 31 ltd.
You can buy an ƒ1.4 lens for any reason you want. Did you buy yours to use only at ƒ1.4?
Or more to the point...
Have you actually compared the lenses or is this all done by comparing charts done with different camera bodies? Without regard to lens sample size, sample variation etc. I look at the LensTips 31 example. It's awful. I've seen much better out of a 31.


As I said, Digitalis had a testing bench, why do you take Lens Tip over his testing?
Because you don't like his results?

As tie breaker, how about PC Mag

FA 31, 4 stars, rated excellent... https://www.pcmag.com/review/299492/pentax-smc-fa-31mm-f-1-8-limited
Sigma F1.4 ART 3.5 stars rated good. https://www.pcmag.com/review/329230/sigma-30mm-f1-4-dc-hsm-art

It looks like you'll do pretty good with either.... but conclusions on which is better I'll save for users like digitalis who have tested the lens on the same Pentax body.

Last edited by normhead; 04-26-2019 at 11:34 AM.
04-26-2019, 11:40 AM   #19
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@norm
Why do you take his examples?
I'll always take independent sites test than tests from someone who is too invested in any kind of gear.
Yes 31 ltd tests at lenstip are awful. Isnt that telling something? Lens variations? Couldnt Digitalis have same issue with the sigma one?
Thats the same reason why i dont go to fuji forums for tests of my fuji gear or nikon forums for tests of my (ex) nikon gear.
If i'd want to stop down why wouldnt i use DA 35 2.4 its better or equal than both 31 ltd and sigma 30 1.4 throughout all its aperture range? Why pay a premium for ltd?


@gatorguy - yes sigma 30 f1.4 autofocus isnt what id call reliable.


Last edited by Trickortreat; 04-26-2019 at 11:49 AM.
04-26-2019, 12:31 PM   #20
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QuoteOriginally posted by Trickortreat Quote
@norm
Why do you take his examples?
I'll always take independent sites test than tests from someone who is too invested in any kind of gear.
Yes 31 ltd tests at lenstip are awful. Isnt that telling something? Lens variations? Couldnt Digitalis have same issue with the sigma one?
Thats the same reason why i dont go to fuji forums for tests of my fuji gear or nikon forums for tests of my (ex) nikon gear.
If i'd want to stop down why wouldnt i use DA 35 2.4 its better or equal than both 31 ltd and sigma 30 1.4 throughout all its aperture range? Why pay a premium for ltd?


@gatorguy - yes sigma 30 f1.4 autofocus isnt what id call reliable.
You don't know Digitalis do you? He's tested almost every lens under the sun, and he's quite impartial, but, thats why I went to best two out of three. We know of one guy who has had both lenses in his hands and tested them on the same camera body. That puts him way ahead of everyone else in my mind. The two other sites are divided, but the big draw back they listed for the K-1 was vignetting on the K-1. I'm betting the Sigma vignettes worse on aK-1 than the 31 does.

Last edited by normhead; 04-26-2019 at 12:38 PM.
04-26-2019, 09:26 PM   #21
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Thank you all for your replies. Interesting comparison site

This is the first chance I've had to get back to the thread. Thank you all for your input. I appreciate it. Meanwhile I've visited lots of camera comparison sites and found one that I really like - cameradecision.com. I did a one-on-one comparison of the K-70 which I have and the Sony Alpha 7 III. Here's the result:

Sony A7 III vs Pentax K-70 Detailed Comparison

I have no idea what you professionals think of this link and of the validity of the comparisons but I thought it was a pretty handy site. Down near the bottom under "Our Decision" the K-70's imaging score was 62 vs the Sony's 81. I know, I know. The Sony is much more expensive and I suppose the comparison isn't fair but it leaves me with serious doubt about the K-70.

I told my photography teacher that I would send him samples of photos taken with all three lenses (excluding the macro) under ideal conditions - highest practical shutter speed, on a tripod using a remote shutter release - so he can see where I'm going wrong. I won't have a chance to do that tomorrow but hopefully Sunday, then I'll post some here. I don't know how to include the data you want to see. So stay tuned.
04-26-2019, 09:39 PM - 1 Like   #22
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QuoteOriginally posted by Joyce Keay Quote
This is the first chance I've had to get back to the thread. Thank you all for your input. I appreciate it. Meanwhile I've visited lots of camera comparison sites and found one that I really like - cameradecision.com. I did a one-on-one comparison of the K-70 which I have and the Sony Alpha 7 III. Here's the result:

Sony A7 III vs Pentax K-70 Detailed Comparison

I have no idea what you professionals think of this link and of the validity of the comparisons but I thought it was a pretty handy site. Down near the bottom under "Our Decision" the K-70's imaging score was 62 vs the Sony's 81. I know, I know. The Sony is much more expensive and I suppose the comparison isn't fair but it leaves me with serious doubt about the K-70.
The Sony is a "full-frame" camera - its sensor is 50% larger than the K-70's sensor. Regrettably, Pentax doesn't make a 24mp "FF" camera, but the K-1ii would be a better comparison - and here the comparison is 89 vs 91, a virtual tie {and price comparison is similar}
Sony A7 III vs Pentax K-1 II Detailed Comparison
04-27-2019, 07:05 AM   #23
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QuoteOriginally posted by reh321 Quote
The Sony is a "full-frame" camera - its sensor is 50% larger than the K-70's sensor. Regrettably, Pentax doesn't make a 24mp "FF" camera, but the K-1ii would be a better comparison - and here the comparison is 89 vs 91, a virtual tie {and price comparison is similar}
Sony A7 III vs Pentax K-1 II Detailed Comparison
The K-1 kills it in imaging and value. Where the A7iii picks up it's advantage is features (read things that don't get you good images) and size. But, if you don't want a tiny little camera that doesn't fit your hand, the K-1 kills the A7iii.

If you shoot a lot of landscapes the A7iii has little to offer.
Hard to understand how a mainstream site doesn't understand, many of us don't think small size is good thing.

This site caters to snapshot shooters.

04-27-2019, 10:21 AM   #24
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QuoteOriginally posted by normhead Quote
The K-1 kills it in imaging and value. Where the A7iii picks up it's advantage is features (read things that don't get you good images) and size. But, if you don't want a tiny little camera that doesn't fit your hand, the K-1 kills the A7iii.

If you shoot a lot of landscapes the A7iii has little to offer.
Hard to understand how a mainstream site doesn't understand, many of us don't think small size is good thing.

This site caters to snapshot shooters.
Yeah, the A7 III has only 24Mp.



04-27-2019, 12:52 PM   #25
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QuoteOriginally posted by normhead Quote
You don't know Digitalis do you? He's tested almost every lens under the sun, and he's quite impartial, but, thats why I went to best two out of three. We know of one guy who has had both lenses in his hands and tested them on the same camera body. That puts him way ahead of everyone else in my mind. The two other sites are divided, but the big draw back they listed for the K-1 was vignetting on the K-1. I'm betting the Sigma vignettes worse on aK-1 than the 31 does.
Of course. Sigma 30 is a crop lens while 31ltd is ff. No reason to use or test sigma on k1
04-27-2019, 05:04 PM   #26
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QuoteOriginally posted by Trickortreat Quote
Of course. Sigma 30 is a crop lens while 31ltd is ff. No reason to use or test sigma on k1
From what I've seen, no one has any cause to be upset, regardless of what they own. Except fo the link you posted , they appear to be really close. The weird thing bing, in the link you posted the 31 had more resolution as they measured it, but it looked softer. It wasn't even internally consistent.
04-27-2019, 07:13 PM   #27
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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.
The 55-300 and 18-135 are very highly regarded consumer zooms. Both are weakest at the longest focal lengths of their ranges, but are generally excellent and certainly comparable to similar offerings from other brands. They are sharpest a stopped down a little.

The DA 40 Limited and DFA100 macro are exceptionally sharp, even wide open.

If you are not getting sharp results you are either not focussing accurately or not holding the camera steadily enough. Changing cameras or brands will not fix that. Comparing the K-70 to the Sony A7 III is like comparing a four cylinder commuter to a V8 grand tourer.

Please post some images (with intact exposure information) to this thread and we'll do our best to help diagnose your problem.
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