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06-20-2011, 07:33 AM   #31
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Again, I just love the way the right side of the 50mm just renders (I think you've switched the prime to the right with the second 50 set), when it comes to the 50, I definitely like the right side among the full image, it's almost got the 3D look (not quite but getting there) which the images on the left totally lack in the full image.

35 is darn close...but then again I've had the FA35/2 and eventhough it has better MTF than the 31/1.8 limited (which I also had) the latter is a much better lens...at the end of the day, it's obvious MTF figures doesn't even come close to telling the whole story.

06-20-2011, 08:41 AM   #32
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Thanks for posting the full images. I personally find the images from the primes and the zoom to be almost indistinguishable. And other than the 50mm f/2.8 shot, I found the 100% crops to be too close to call. And there's no big bokeh advantage for the primes either, with all three of the lenses producing nice creamy background blur.

Despite all the true-believers on here, I still fail to be entirely convinced that there is a significant image quality difference between prime lenses and the best modern zooms. I regard primes as being most useful for specialty purposes that are not practical to achieve in a zoom...macro capabilities, very large aperture, very compact dimensions, etc. But of course, I don't own any primes yet, so it's possible that I could change my opinion in the future.

As for the disappointing 50mm f/2.8 results from the Sigma 17-50mm, I expect that it's either an error in testing methodology, or (perhaps less likely, since all the other pictures look fine) a problem with that particular lens. I've owned and shot with several zooms at 50mm and f/2.8, including the Tamron 17-50mm, Tamron 28-75mm, and the Sigma 50-150mm, and they've all produced good, sharp images at 50mm f/2.8. I think that if the new Sigma 17-50mm was seriously deficient at this important focal length, that the professional reviewers would have picked up on it. But I haven't seen that.

As someone else pointed out, it is extremely easy to make a misstep when shooting comparison images between lenses, so I now mostly try to use real world images to evaluate a lens.
06-20-2011, 10:13 AM   #33
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QuoteOriginally posted by pcarfan Quote
I second that, even a fraction of a twist to the focus ring (less than a mm) makes a big difference....so much so I don't do much of it any more as it is highly vexing.
Agreed. And I've rep'd you for using the word "vexing".
06-20-2011, 10:32 AM   #34
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pop4,

Thanks for the test images. Looking at the MTF results of the 17-50, I see that that they are quite consistent throughout the zoom range. Wide primes are not, in general, as "sharp" as longer lenses, MTF scores peaking in the 50-100mm range. So I would not expect the zoom to match the 50mm prime. At 35mm, the Sigma zoom does quite well against an excellent prime, especially stopped down. I wonder how much of the FA35's apparent sharpness edge results from higher contrast, which is ammenable to post processing. The FA35mm do look more contrasty to me.

06-20-2011, 12:24 PM   #35
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thanks and I have the same observation that the primes are definitely better. having said that, the zoom is not far behind which is really nice as well. I believe each lenses have their use. the zoom for it's versatility and the primes for fast aperture and better IQ. I think the great potential of the prime sales would rely heavily on the compactness factor nowadays. although fast aperture would remain as the main selling point.
06-20-2011, 03:36 PM   #36
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Thanks a lot for posting the full images.

I also prefer the right hand side images in the 50mm comparison.

In any event, the Sigma zoom is very impressive, AFAIC. Too bad that Pentax shooters have to buy the OS whether they want it or not.
06-20-2011, 05:29 PM   #37
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QuoteOriginally posted by pcarfan Quote
(I think you've switched the prime to the right with the second 50 set)
Whoops, that's right, I didn't mean to do that. But what I did mean to do, and did, was switch the prime to the right for the 35mm shots in the 2nd set. So in the 2nd set, the shots from the prime lenses are on the right. I wonder how many people picked up on that for the 35mm comparison...

QuoteOriginally posted by Pentaxor Quote
I think the great potential of the prime sales would rely heavily on the compactness factor nowadays. although fast aperture would remain as the main selling point.
QuoteOriginally posted by Edgar_in_Indy Quote
I regard primes as being most useful for specialty purposes that are not practical to achieve in a zoom...macro capabilities, very large aperture, very compact dimensions, etc.
It's quite interesting that both of you mentioned compactness as one of the advantages primes have over zooms, but personally, it's not something that bothers me. Here are the three lenses I used in the testing before, the Pentax FA 35mm F2.0, Sigma 17-50mm F2.8 and Sigma 50mm F1.4, with a Sigma 85mm F1.4 thrown in for good measure. The images are processed intentionally to crush the blacks and to hide detail in the lenses. Can you tell me which lens is which?




What if I put the lens hoods on, maybe that will help a bit:


Last edited by pop4; 06-20-2011 at 06:09 PM.
06-20-2011, 07:53 PM   #38
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I know that the Sigma 85mm is a huge lens, but that is by design. It would be hard to have a lens that's both compact AND has a superwide aperture AND does not have extremely bad vignetting. That's the thing about lenses, they are all a set of compromises. Every single lens out there makes some big compromises.

That's why there will never be THE perfect lens. It just depends on what is important to you. For my shooting, I like the versatility of a zoom. Which is why I find it encouraging that modern zooms, such as the subject of this thread, are so capable.

Compactness isn't necessarily a trait of a prime, but it CAN be. But that will require some compromises. A compact prime with a large aperture will have some wicked vignetting.

06-20-2011, 09:06 PM   #39
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Left to right:

85/1.4 >> 35/2 >> 17-50/2.8 >> 50/1.4
06-20-2011, 09:18 PM   #40
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QuoteOriginally posted by Edgar_in_Indy Quote
Compactness isn't necessarily a trait of a prime, but it CAN be. But that will require some compromises. A compact prime with a large aperture will have some wicked vignetting.
I have the similar understanding that you do. although the Sigma 85 is obviously fatter and quite long (by virtue of design and Sigma brand), they could make it compact and might have to deal with certain compromises. the M85, DA70 and FA77 for example are significantly smaller and more compact, and at the same time can get the job done. although they are significantly slower in aperture speed, I know they can find a way to atleast make the smaller as opposed to zooms which I don't think can go any more smaller than primes. to make the prime lens significantly smaller, they have to decrease the number of elements, design a new optical formula, emphasize on external focus barrel extension rather than IF design and finally sensor size compatibility. I would think that they could design a compact fast 85mm exclusively for the APS-C which would greatly reduce the form and size factor of the lens. Samsung however has a longer 85mm but atleast a bit thinner than the Sigma 85 and could be IF a well. as to why Samsung designed such a big lens rather than compact, we can only speculate an FF capability of the lens in question, which there is a possibility of FF camera?
10-01-2011, 02:17 AM   #41
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In real life...

I love 'pixel peeping', I enjoy comparing reviews and test results, I love reading arcane photo articles online or in magazines, and I come from a history of firm belief in the superiority of prime lenses, BUT I found that more and more I would go out with just a (Canon) compact in my pocket.

My famous brand name bag with Pentax DSLR, Battery Grip, prime lenses, filters, flash, remote release etc.etc.etc. stayed home time after time.

Now I have a K-5 fitted with a Sigma 17-50. The compact lives at home, and the camera comes out with me nearly every day, with just a spare battery and Polariser filter in my pocket.

I am VERY happy with this camera/lens combination and the pictures it gets me. Some prime lenses sold on Ebay already, just the (Samsung version) 35mm f2 to go, along with my trusty 16-45 Pentax.

Graham.
07-21-2012, 11:53 AM   #42
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..and STILL happy with the 17-50mm........
02-05-2013, 08:12 AM   #43
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Tamron 17-50 2.8 prime lens

This is a very interesting discussion because I have had the thought several times in using my Tamron 17-50mm 2.8 that having it mounted on my K-7 is like carrying a bagful of 34 different prime lens! Using it is making me feel disloyal to my 43 mm ltd, to my DA 50 macro 2.8, the only two primes I have in the 17-50 range. The lens does not perform as well on the K-10 and K-20, particularly in low-light situations. On the K-7 the Tam 17-50 will take a nice photo in an almost dark room, I suppose because the K-7 just has more ISO range to offer (when set on green mode, I mean). I think for special occasions like maybe a planned portraiture session, the primes will always take precedence over zooms, but those occasions will tend to get fewer and fewer as excellent zoom lens become good enough, or even better than good enough.
02-05-2013, 10:33 AM   #44
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QuoteOriginally posted by Class A Quote
In any event, the Sigma zoom is very impressive, AFAIC. Too bad that Pentax shooters have to buy the OS whether they want it or not.
Not so. I bought this lens to pair with my K-5 IIs. The Pentax version does *not* have OS on it. You can see where that switch would be on the lens body, but it's just not there. While it's not clearly stated in any online sales description that I have yet to see, on B&H's site, if you go to the specifications tab on the lens' site, it does show that the lens is not optically stabilized.
02-05-2013, 11:48 AM   #45
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QuoteOriginally posted by azcavalier Quote
Not so. I bought this lens to pair with my K-5 IIs. The Pentax version does *not* have OS on it. You can see where that switch would be on the lens body, but it's just not there. While it's not clearly stated in any online sales description that I have yet to see, on B&H's site, if you go to the specifications tab on the lens' site, it does show that the lens is not optically stabilized.
So how do you like the lens? Say compared to the pentax kit lens 18-55mm?
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