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07-25-2008, 07:24 AM   #1
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pentax 12-24 or sigma 10-20

which is better optically. pentax 12-24 or sigma 10-20
in this forum is valued at best sigma (9.29), even better is valued at Pentax 10-17 (9).
The Pentax 12-24 is worth the 8.86.
but I have heard that the best is the Pentax 12-24.
which buy?

07-25-2008, 08:05 AM   #2
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That's a hard question. Poke around the forums and I think there have been several previous discussions on this. I'm interested in this topic as well and have done my share of reading. The consensus seems to be that they are both great lens, but that the Pentax 12-24 is the better lens. That said the Sigma 10-20mm is an excellent performer, especially for the price. To make the choice harder there's a Tamron 10-24mm coming out soon (maybe by the end of the year). Good luck choosing.

Some links:
Sigma 10-20mm reviews here at Pentax Forums
Pentax 12-24mm review here on site
Photozone Pentax 12-24mm review
Photozone Sigma 10-20mm review
07-25-2008, 08:29 AM   #3
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I looked at the sigma 10-20, the pentax 10-17 fisheye, and the pentax 12-24.

Ultimately I took the sigma and am glad because my analysis of shooting style has shown that 20% of all photos are done with this lens, and 12% of all photos I take are at 10mm. I would miss the range 10-12mm if I did not have it.
07-25-2008, 08:56 AM   #4
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I have read every post on this subject here and elsewhere -- and boy there are a lot! I think I can rightly boil down all the information into four salient facts:

1. Either lens is fine for most uses. They work and produce great images.

2. The Pentax 12-24mm is optically superior for cases where it really matters (eg: pro-level property photography).

3. The Pentax 12-24mm has enough of a range that it can be a walk around lens for those that favour the wide end. (After all some photogs used nothing but 28mm or 35mm on full frame.)

4. The Sigma 10-20mm is great value for money and has the extra 2mm that some find essential.

Basically, if you want to save money, need the extra 2mm and don't mind that in that range you will get significant barrel distortion at the edges, buy the Sigma.

I have just obtained a 77mm B+W circular polariser, ready for the day when I can afford one or the other. For now a 67-77mm step-up ring will bind it to my 16-45mm.

07-25-2008, 09:41 AM   #5
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QuoteOriginally posted by rparmar Quote
I have read every post on this subject here and elsewhere -- and boy there are a lot! I think I can rightly boil down all the information into four salient facts:

1. Either lens is fine for most uses. They work and produce great images.

2. The Pentax 12-24mm is optically superior for cases where it really matters (eg: pro-level property photography).

3. The Pentax 12-24mm has enough of a range that it can be a walk around lens for those that favour the wide end. (After all some photogs used nothing but 28mm or 35mm on full frame.)

4. The Sigma 10-20mm is great value for money and has the extra 2mm that some find essential.

Basically, if you want to save money, need the extra 2mm and don't mind that in that range you will get significant barrel distortion at the edges, buy the Sigma.

I have just obtained a 77mm B+W circular polariser, ready for the day when I can afford one or the other. For now a 67-77mm step-up ring will bind it to my 16-45mm.
I have looked and looked at all the thousands of images I have done with my sigma at 10mm and have only one question. What significant barrel distortion?

I simply don't see it. You do see typical wide angle distortion i.e. exageration of details due to perspective, but I don't see any bending of lines like that of a fish eye.

But then again my glasses are so strong that if I am not careful, buildings look curved anyways
07-25-2008, 09:55 AM   #6
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QuoteOriginally posted by Lowell Goudge Quote
I have looked and looked at all the thousands of images I have done with my sigma at 10mm and have only one question. What significant barrel distortion?

I simply don't see it. You do see typical wide angle distortion i.e. exageration of details due to perspective, but I don't see any bending of lines like that of a fish eye.

But then again my glasses are so strong that if I am not careful, buildings look curved anyways
Sigma AF 10-20mm f/4-5.6 EX DC (Pentax K) - Review / Test Report

QuoteQuote:
The Sigma AF 10-20mm EX DC showed a rather unusual distortion characteristic. At 10mm most of the image field is almost free of distortions so the measured distortions figures look fairly fine here (taken a little inward from the borders). However, this is only part of the truth. If you check the 10mm distortion chart below you will notice that the extreme corners are actually quite (barrel-)distorted - probably in the 2-3% range. At 14mm the lens shows a moderate degree of pincushion distortions, less so at 20mm.
but still 2-3% is not that bad @ 10mm
07-25-2008, 09:56 AM   #7
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From another point of view there is also the ultra-wide prime. I have the DA14 f/2.8 and I'm very impressed by the lack of distortion for an ultra-wide. What little distortion there is can be corrected very easily. Price-wise it falls between the Sigma 10-20 and Pentax 12-24.

Oh, why I chose the DA14 over the other 2 lenses; I wanted f/2.8 and I find myself more of a prime user. The DA14 focuses very fast and accurate as well.
07-25-2008, 10:16 AM   #8
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QuoteOriginally posted by deejjjaaaa Quote
I guess the question is, define significant.

for me, who gives a s&$# if there is 2% distorton only at the extreme corners.

This is something you will only see if and only if your subject is a piece of paper with a 1/4 inch line grid and you take your shot perfectly parallel to that grid.

for practical terms the lens is just fine. the real problem with tests is we can measure all sorts of things that are totally meaningless. I think this is one such case

07-25-2008, 10:59 AM   #9
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is also important for my light. Pentax is the f / 4, the sigma is a 5.6 to 20mm.
the sigma 10-20 = 350 mm €
I found the Pentax 12-24mm = 410 €
only 60 €
07-25-2008, 12:41 PM   #10
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QuoteOriginally posted by Lowell Goudge Quote
I guess the question is, define significant.

for me, who gives a s&$# if there is 2% distorton only at the extreme corners.
But please recognise that some do care. One example I came across was an editor for a national magazine who needs accurate interior shots. They use the Pentax lens for that reason after trying the Sigma and saying "not good enough". They have done thousands of shots at a pro level. I guess I should take their opinion into account.

(Can't find the reference off-hand but it was on another web forum.)

Please read my No. 1 point. I am not trying to knock your favourite lens. But the OP did ask "which is better optically".
07-25-2008, 12:49 PM   #11
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QuoteOriginally posted by rparmar Quote
But please recognise that some do care. One example I came across was an editor for a national magazine who needs accurate interior shots. They use the Pentax lens for that reason after trying the Sigma and saying "not good enough". They have done thousands of shots at a pro level. I guess I should take their opinion into account.

(Can't find the reference off-hand but it was on another web forum.)

Please read my No. 1 point. I am not trying to knock your favourite lens. But the OP did ask "which is better optically".
No offence intended, but for that precision, you would not be using a DSLR but a medium or large format with tilt and shift. that is the only way to get accurate interior shots.

the perspective distortion alone from a DSLR would make the shots too difficult to manage without doing perspective correction in post processing, and in that process, the corners fall out in the crop anyway.

I have used the 10-20 for tons of interior shots, and that has never been an issue. In fact, I would be really interested to see a comparison of the 10-20, at 10mm but cropped to 12, compared to the 12-24 without cropping. I would be willing to bet the cropped 10-20 would be better than the extremes of the 12-24.

What is more important is the point made by revinhood, the extra stop in terms of speed. I have often found myself inside an old dimly lit cathedral with the camera held against a post, or sitting on top of a pew for stability. an extra stop, yeah that might be of interest, but then again SR does a really good job too.
07-25-2008, 08:57 PM   #12
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These 2 have been routinely debated, but never has a side by side comparison been shown (that i know of). I have the sigma 10-20mm and shoot real estate photos part time, which has paid for my camera gear, plus expenses as well as my last 3 two month long trips to florida for the winter (does this qualify the lens as good enuff for professional work?). The 10-20mm at 10mm will require some practice to prevent distorted perspective or the use of a corrective program like photoshop, but this distortion can also be seen at 12mm in both lenses under some circumstances. The pentax is slightly sharper at the edges and faster. The sigma can be found for $150-$200 less than the Pentax. As to which is better?, for me, its the sigma.....Only you can answer that one for yourself. I would suggest that you rent each of them for a couple of days and then decide.
07-26-2008, 02:01 AM   #13
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QuoteOriginally posted by Lowell Goudge Quote
No offence intended, but for that precision, you would not be using a DSLR but a medium or large format with tilt and shift. that is the only way to get accurate interior shots.
From my theoretical perspective I would agree. I think in this case there was a cost factor involved. Outfitting a team of photographers with Pentax is a lot cheaper than other SLRs, let alone medium format. That is where Pentax really shines, no matter which lens is used.
07-26-2008, 06:34 AM   #14
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I will add my two cents: I cannot compare the Sigma with the Pentax, as I have opted for the Sigma. My reasoning was as follows:

– 10mm offers a significantly wider view, than 12mm
– the Sigma is a rectilinear lens, not a fish-eye (the Pentax 10-17mm is something so different, it shouldn't be compared with the two other lenses, here)
– the distortion at 10mm is low, noticeable in interieurs and architecture, but low
– In all the pics I have seen, I cannot see an advantage of the Pentax at comparable focal lengthes – do not compare the Sigma's 10mm end versus the Pentax 12mm end, these are diffferent worlds.

I had enough other wide lenses to cover my needs from 15mm and longer, so the 10mm added more value for me, than the 12mm.

The Sigma is nicely finished, the remaining optical distortion (low) can be corrected in post-processing and perspective distortion is a thing, all wide angle lenses share, because this is not a shortcoming but a simple result of the photogs position.

Stepped down to f8, the Sigma is a superb performer (considering the short fl) and even if there might be "better" lenses. I wouldn't care, as the Sigma is good enough.

The only drawback is, that it gets very dim at f/5.6 on the 20mm long end. Having a constant aperture of f/4 is the only real advantage I can see with the Pentax. But that is literally outweight by the Sigma, because it is comparatively lightweight and small - much, much smaller, than my Sigma 15-30, which I have for film.

regards
Ben
07-26-2008, 07:29 AM   #15
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QuoteOriginally posted by Ben_Edict Quote
The only drawback is, that it gets very dim at f/5.6 on the 20mm long end. Having a constant aperture of f/4 is the only real advantage I can see with the Pentax. But that is literally outweight by the Sigma, because it is comparatively lightweight and small - much, much smaller, than my Sigma 15-30, which I have for film.
The Pentax 12-24mm is actually 30g lighter than the Sigma 10-20mm.
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