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02-16-2016, 11:39 PM   #16
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QuoteOriginally posted by ScooterMaxi Jim Quote
Pretty much all lenses are going to be decent at f/8 in the center, but the zoom is already pretty strong at the edges, and the Sigma leaves something to be desired. When not used for landscape, the wider apertures need to be considered.

At f/4 (wide open on the zoom, stopped down a stop on the Sigma), we have the zoom pretty far ahead - 2296 vs. 2063 in the center, 1959 vs. 1799 at the edge. The zoom sharpness actually peaks by f/5.6 at 24mm - which is unusual for a consumer zoom....
the o.p. specifically asked about landscape usage...

all of those numbers are from the k10d, where is the rez data from a modern camera? or from a ff camera?

well, for ff testing, we can look at what i guess is film in 1985, against a bunch of other 24mm lenses: http://www.kameradoktor.de/testsigma24.jpg

i can't read german, but i can see that the color bars on the sigma lens are taller than almost all of the other lenses translator please? lol

QuoteOriginally posted by ScooterMaxi Jim Quote
The CA is a concern, but easily addressed in raw conversion - particularly so because it is the yellow-blue variety.
no, even the easiest ca removal is never perfectly clean.

both the vignetting and the ca on that zoom will be worse on ff, i suspect that putting it on a 36mp camera is going to be a marginal situation.

QuoteOriginally posted by ScooterMaxi Jim Quote
Many of newer Sigma lenses are very good, but the 24mm from the late '80s doesn't seem to rate all that well. It might "work" on FF digital, but I doubt the edges will be adequate for landscape at any aperture.
that's not what the color foto magazine test seems to indicate, and it definitely doesn't agree with the general consensus:

the lens has a 9.0 rating for sharpness here on the forum: Sigma 24mm F2.8 Super Wide II Lens Reviews - Sigma Lenses - Pentax Lens Review Database

the af version got a 9.6 rating for sharpness: Sigma 24mm F2.8 AF Super Wide II Lens Reviews - Sigma Lenses - Pentax Lens Review Database

the sharpness rating here is a 4.51 out of 5, from seventy reviewers: Sigma 24mm Super Wide II F2.8 A-mount alpha lens reviews

i compared the af version at f/8 on the a7r, full-width center crops, using my standard landscape shot, blow the test photo up to 100%: 24mm camera lens shootout, on the Sony a7R: first round

02-17-2016, 01:06 AM   #17
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If you're sure you're not going to use it then sell it. I love mine and regret not keeping the manual focus version when I bought the AF one. The AF version doesn't feel nearly as good when focusing manually.

I mainly use mine on film cameras where it's the widest lens I have (joint widest if you include the Minolta 24/2.8).
02-17-2016, 07:17 AM   #18
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The big thing is that the Sigma is small and goes down to f/2.8, something the zoom isn't and can 't

For that reason alone I think it's worth having if you, like me, like a versatile walkaround prime in just the right focal length for street and casual photography, with overall pretty good quality. If that's not your bag, and you only walk around with zooms, by all means sell it. Now's a good time to sell full frame lenses
02-17-2016, 10:33 AM   #19
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QuoteOriginally posted by osv Quote
the o.p. specifically asked about landscape usage...

all of those numbers are from the k10d, where is the rez data from a modern camera? or from a ff camera?

well, for ff testing, we can look at what i guess is film in 1985, against a bunch of other 24mm lenses: http://www.kameradoktor.de/testsigma24.jpg

i can't read german, but i can see that the color bars on the sigma lens are taller than almost all of the other lenses translator please? lol



no, even the easiest ca removal is never perfectly clean.

both the vignetting and the ca on that zoom will be worse on ff, i suspect that putting it on a 36mp camera is going to be a marginal situation.



that's not what the color foto magazine test seems to indicate, and it definitely doesn't agree with the general consensus:

the lens has a 9.0 rating for sharpness here on the forum: Sigma 24mm F2.8 Super Wide II Lens Reviews - Sigma Lenses - Pentax Lens Review Database

the af version got a 9.6 rating for sharpness: Sigma 24mm F2.8 AF Super Wide II Lens Reviews - Sigma Lenses - Pentax Lens Review Database

the sharpness rating here is a 4.51 out of 5, from seventy reviewers: Sigma 24mm Super Wide II F2.8 A-mount alpha lens reviews

i compared the af version at f/8 on the a7r, full-width center crops, using my standard landscape shot, blow the test photo up to 100%: 24mm camera lens shootout, on the Sony a7R: first round
I would have to guess (educatedly) that quality control is a huge factor in the variance of the Sigma lenses from that era and how they are rated, but the Photozone tests you quoted clearly show that the Pentax sample is far sharper than the Sigma sample when you look at the full set of scores. (Few people shoot the 24mm FoV on crop only as a landscape lens; and the numbers for the DA at 24 are best at f/5.6 so shooting the lens at f/8 is not ideal even for landscape work.)

As an owner of the DA, I have found the CA correction to be easy and good and not as significant as the raw numbers would indicate, but I agree with you that CA is always an issue and is never perfectly correctable - and that is exactly why I agreed that it is a valid "concern." For sure the DA would be nearly useless on FF - no question about that...

As for users on this forum, pretty much everyone grades on a curve greatly influenced by pricing. The Sigma is a $100 lens rating 8.67 overall, and the Pentax is a $200-250 lens rating 8.63 - discounted in large part due to the marginal build and unusual barrel extension at the wide end. Not sure I could go strongly on user impressions, but if you must then it should be Pentax because at least the mount is in common. The dyxum forum is mostly Minolta/Sony, so that's getting pretty darn far afield.

02-17-2016, 12:32 PM   #20
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the glass is the same regardless of what mount it's in, so the dyxum ratings are just as valuable as the ratings here on pf, really even more so, because it's a sample size of 70 people.

qc on this sigma is indeed a problem, which is why i keep asking the o.p. for samples... if you get one of these lenses, or really any lens, you better know how to test it, like i did in that landscape test.

you can see in that test that the sigma absolutely destroys the pentax smc 24/2.8, it's a far better choice for landscape shooting, but i think that the center contrast on the pentax is probably better.
02-17-2016, 03:25 PM   #21
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QuoteOriginally posted by osv Quote
the glass is the same regardless of what mount it's in, so the dyxum ratings are just as valuable as the ratings here on pf, really even more so, because it's a sample size of 70 people.

qc on this sigma is indeed a problem, which is why i keep asking the o.p. for samples... if you get one of these lenses, or really any lens, you better know how to test it, like i did in that landscape test.

you can see in that test that the sigma absolutely destroys the pentax smc 24/2.8, it's a far better choice for landscape shooting, but i think that the center contrast on the pentax is probably better.
Some of the top lens review sites warn against comparing lenses in different mounts. This is probably especially important when it comes to the wider lenses because flange distance becomes a more-critical calculation in the lens designs. The glass probably does match, but flange distance will have an optimal setting that might or might not closely match Pentax.

A secondary consideration is the difference in expected coloration. Although I never really thought of this as a critical concern, it becomes more evident to me over time. One lens I owned - the Sigma 15-30 - was very difficult to color correct in challenging lighting situations (near dusk, for instance). It is widely viewed that Sigma tends to engineer glass/coatings toward the cooler or even yellower spectrum, although that sentiment has somewhat mellowed in recent years. My experience with various Canon and Pentax optics has shown a pretty strong tendency for the Pentax optics to be warmer.
02-17-2016, 05:21 PM   #22
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QuoteOriginally posted by ScooterMaxi Jim Quote
Some of the top lens review sites warn against comparing lenses in different mounts.
no, they warn against comparing mtf measurements of imaging systems, not lenses because of flange distance.

if flange distance was a problem, as you claim, why is pentax oem'ing the same tamron zooms that canikon uses, for the new pentax ff camera.

it's the distance to the rear element of the lens that could be an issue, with certain lens designs, not the flange distance.

the sigma superwide ii ratings on a-mount are just as valid as they are on k-mount, or any other lens mount... they all say the same thing; the lens is sharp.

lens coloring with pentax lenses is all over the map, look at how yellow the old 50/1.4 taks are... it's not a factor in image sharpness.
02-17-2016, 08:22 PM   #23
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I've tried to be nice.

The Sigma is a $100 lens because it isn't sharp along the edges in crop mode, let alone in the corners - and it is poor on FF, even on film and more so on digital (look closer at your unprocessed images). The DA 16-45 is clearly sharper, held to better tolerances (despite poor build) and commands prices twice as high accordingly. Market rules for good reason here.

Optical designs get shared, but the actual physical implementation on the better lenses are invariably reworked. Some of the lesser designs are rebranded wholesale, and that will be a problem for Pentax and Tamron if such an arrangement results in improper premium pricing. We don't know that yet.

Bringing up Taks is a diversion. Where is a Tak in this comparison?

02-17-2016, 10:18 PM   #24
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QuoteOriginally posted by ScooterMaxi Jim Quote
I've tried to be nice.
that may be true, but you've also made claims that the vast majority of lens reviewers don't agree with, and in the case of the flange distances for example, are flat-out wrong... the only "physical implementation" that'll be done is altering the distance from the lens group to the lens flange, in order to equalize the distance to the sensor... it's nothing more than a permanent adapter.

you continue to claim that the superwide ii isn't sharp, when the color foto lens test proved how sharp it is.

neither you nor the o.p. has posted even one single photo to back up anything that you two have said.
02-18-2016, 06:15 AM   #25
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QuoteOriginally posted by osv Quote
... you continue to claim that the superwide ii isn't sharp, when the color foto lens test proved how sharp it is.

neither you nor the o.p. has posted even one single photo to back up anything that you two have said.
I'd love to see some shots that exhibit issues with this lens. I have had this on my own personal roadmap of lenses for a while now and this thread has been very interesting to me.
02-18-2016, 09:47 AM   #26
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QuoteOriginally posted by pres589 Quote
I'd love to see some shots that exhibit issues with this lens. I have had this on my own personal roadmap of lenses for a while now and this thread has been very interesting to me.
here are a couple of three-way comparisons, full-width crops on the a7r, be sure and view the pics at 100% 24mm lens sample variation: Three Sigma 24mm lens and three Canon FDn 24mm lenses compared

that's how i check wide lenses for decentering and such, for example i have three pentax 50/1.4 lenses that are all slightly off on one side or the other.

copy variation trumps just about everything.
02-18-2016, 11:15 AM   #27
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I don't want to post about the Sigma lens anymore - no one will win that argument here.

However, I can't let go the blissful ignorance regarding requirements for retrofocus design of wide angle lenses due to flange distance without some fact sharing. The longer the distance, the greater bending of light rays requires more elements and complexity in design. Despite its seven element, five group design, an Elmarit-M 24/2.8 lens will yield sharper results with less CA than any 24mm lens designed for FF cameras with a mirror because of the simple physics regarding bending light rays. By logical extension, the shorter the flange distance, the less complexity and bending required. Third-party lens designs require accommodation for the longest anticipated flange distance to cover the sensor distance without hard vignetting.

See: Comparing the Design and Quality of Mirrorless Cameras with DSLRs

(Ignore the core arguments regarding mirrorless, but the explanation regarding flange distance is clear and correct roughly half way through the video.)
02-18-2016, 01:13 PM   #28
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James - the mount (Canon, Nikon, Pentax, Minolta) for those lenses makes sure that the distance between the rear element of the lens is always at the same distance of the sensor (or film) regardless of the camera it's mounted in. So osv is right in the sense that a mount is nothing but a "permanent adapter" on those 3rd party lenses. If the registration on a Pentax, for example, is 0.46mm longer than the Canon EOS registration distance, the lens for the Pentax will be 0.46mm shorter (the distance being "shaved off" from the mount) so that the lens elements will be at the same distance from the sensor on both mounts. Infinity setting ends up being the same. And the same optical design can be used everywhere.

That's why Adaptall worked, and that is why you can switch mounts on lenses sometimes and infinity works (I've seen Olympus and Minolta lenses swapped to K mounts).
02-19-2016, 11:43 AM   #29
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I get it. The overall design of a particular third party lens will have the same - typically long - focal distance no matter the camera format. Still, the camera reviewers do warn against assuming similar results from the "same" lens comparing between mounts - and that's why the better review sites will review third-party lenses on more than one mount and the results go somewhat beyond sample variation.

Just want to reiterate about the importance of flange distance, though. Native camera lens designs allow the rear element to reach closer to the focal plane if the mount is closer to the film plane. Hence, the old Konica mount allowed for simpler, smaller wide angle lens designs due to the smaller camera box and short flange distance. However, Canon FL and Konica had relatively dull OVFs due to the same limitation. Nikon, Olympus and Pentax tended to be brighter and larger consequently due to the larger mirror box.

The third-party wide angle designs have to account for clearance allowed for the largest mirror box to be incorporated (and resulting flange distance). So, more light ray bending.

I know Adaptall is much loved around here, but having used a few of the lenses back in the day... Tamron had good reason to abandon the concept, and the quality of their engineering improved considerably as a result.

Last edited by ScooterMaxi Jim; 02-19-2016 at 11:58 AM.
02-19-2016, 12:04 PM   #30
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QuoteOriginally posted by ScooterMaxi Jim Quote
Hmm, I'm just not getting through well at all here regarding visualizing the rear element.
that's because the things that you are saying are simply not true, and you refuse to listen and look at the facts that have been presented to you... the color foto magazine testing, for example.

QuoteOriginally posted by ScooterMaxi Jim Quote
I know Adaptall is much loved around here, but having used a few of the lenses back in the day... Tamron had good reason to abandon the concept, and the quality of their engineering improved considerably as a result.
that's wrong again, for example, the sp adaptall-2 180/2.5 compared very well against native glass of the day: Tamron SP Adaptall-2 180mm F/2.5 LD-IF Model 63B

same with this 70-210: Tamron SP Adaptall-2 70-210mm F/3.5-4 Model 52A

the 60-300 adaptall-2 is good on 36mp, after stopping down a bit, the only problem i see with it is a bit too much vignetting.

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