Fred Miranda wrote:
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I didn't formally reviewed the Sigma 90/2.8 but from my tests, both axial and lateral CA are low. It looks like DxO received a dud copy and reviewed it anyways.
My display is the Mac 6K.
I think what might be going on here is that the 90mm does have high lateral chromatic aberration as DxO shows, but that Sigma doesn't let you turn off those corrections in-camera. Dx0 review the raw data before demosaicing, and so get around the baked-in correction. That means both you and DxO are right: the lens is sharper than the 35PMpix figure suggests, after lateral chromatic aberration is corrected.
Also, I think the reason we often seem to disagree on sharpness differences in your test shots, is because I'm looking at a high-end 2K NEC monitor that has been calibrated for accurate soft-proofing. That's a world away from that high ppi monster that is the Retina 6K; I presume you are aware of the difficulties of assessing sharpness on such monitors, as discussed in these links:
Petegh wrote:
I think what might be going on here is that the 90mm does have high lateral chromatic aberration as DxO shows, but that Sigma doesn't let you turn off those corrections in-camera. Dx0 review the raw data before demosaicing, and so get around the baked-in correction. That means both you and DxO are right: the lens is sharper than the 35PMpix figure suggests, after lateral chromatic aberration is corrected.
Also, I think the reason we often seem to disagree on sharpness differences in your test shots, is because I'm looking at a high-end 2K NEC monitor that has been calibrated for accurate soft-proofing. That's a world away from that high ppi monster that is the Retina 6K; I presume you are aware of the difficulties of assessing sharpness on such monitors, as discussed in these links:
The Sigma 90/2.8 has very low lateral CA and that's with all RAW built-in corrections removed.
My point is that although it's not the sharpest 90mm lens and does show some astigmatism, it's still capable of outstanding resolution to the very corners. All that in a very compact lens with AF.
Here is a crop showing the very extreme corner of the frame wide open. (all built-in corrections removed using DNG cleaner)
Fred Miranda wrote:
The Sigma 90/2.8 has very low lateral CA and that's with all RAW built-in corrections removed.
My point is that although it's not the sharpest 90mm lens and does show some astigmatism, it's still capable of outstanding resolution to the very corners. All that in a very compact lens with AF.
Here is a crop showing the very extreme corner of the frame wide open. (all built-in corrections removed using DNG cleaner)
Yeah, that crop certainly looks sharp on my monitor, except perhaps the last 1/3 of the diagonal into the top-left corner.
I've dug a bit more into DxO's results, and it seems the devil is in the detail here: if you look at the 'Chromatic Aberration'>'Field Map' on this page:
it shows that, indeed, lateral chromatic aberration 'is' very low across most of the frame, only deteriorating in the very corners. This might explain why David had sharpness issues in the very corner of his copy; your copy seems better in that regard, so there's definitely some sample variation going on here...
Petegh wrote:
Yeah, that crop certainly looks sharp on my monitor, except perhaps the last 1/3 of the diagonal into the top-left corner.
I've dug a bit more into DxO's results, and it seems the devil is in the detail here: if you look at the 'Chromatic Aberration'>'Field Map' on this page:
it shows that, indeed, lateral chromatic aberration 'is' very low across most of the frame, only deteriorating in the very corners. This might explain why David had sharpness issues in the very corner of his copy; your copy seems better in that regard, so there's definitely some sample variation going on here...
As far as I know, lateral CA only affects the off-axis area. It's never an issue around the center.
I've experienced some variance with this specific lens and one copy had mushy corners. I tried a total of four copies (3 for the E-mount and 1 for the L-mount) and only one was somewhat centered.
Nothing personal to any of my landscape-photo heroes posting above, and seeking pre-forgiveness for ADD-ing somewhat off topic, but I’ve been working on a plan for what to do with some of those mushy-cornered 90mm’s—
Best to all. 🍀🍀😀
A74, 90mm 2.8 Sigma Contemporary—@f:3.5, 1/100sec, ISO 100
Byrd Williams IV, 4th-generation professional photographer, Dallas TX
Fred Miranda wrote:
As far as I know, lateral CA only affects the off-axis area. It's never an issue around the center.
I've experienced some variance with this specific lens and one copy had mushy corners. I tried a total of four copies (3 for the E-mount and 1 for the L-mount) and only one was somewhat centered.
'only one was somewhat centered.'
WTF? Sigma. I don't know what's going on here: on their website, Sigma is claiming that every copy of their 90mm lens is MTF tested before leaving the factory (that was a surprise to me - I thought only the margins on their Art lenses could support such individual treatment).
'As far as I know, lateral CA only affects the off-axis area. It's never an issue around the center'
, its probably because the center ain't really the center Fred - in all those de-centered copies!
Don't get me wrong in everything I've said above: I think the Sigma 90mm is a great little lens - sharp across almost the entire frame, to the point where it wouldn't bother most people about the slight corner issues. Its just a shame to hear about the variability issues (although, its probably unfair to single out any brand on that, as they all still have their problems)
Just grabbed a 24mm F2 yesterday after taking back the Sony 24mm 2.8 and have to say out of C1 the lens profile looks very clean on distortion. Nothing done here and I like how it is holding straight lines. Corners look better too but need to test that
GMPhotography wrote:
Just grabbed a 24mm F2 yesterday after taking back the Sony 24mm 2.8 and have to say out of C1 the lens profile looks very clean on distortion. Nothing done here and I like how it is holding straight lines. Corners look better too but need to test that
I remember this lens being way wider without distortion correction. Perhaps close to 22mm?
The 90 is nice for it's size and weight. It's not a stellar lens but it's better than a smart phone Paired with the 20 and 35 it's a nice add on to make a small kit used on an A7c.
I got Sigma 24mm f/3.5 and Sigma 45mm f/2.8 C. I am thinking about buying the 90mm to complete my super compact kit, but I am not sure if 90mm is the way to go. Sony 85mm f/1.8 is cheaper (used B&S pricing) and faster and not that much heavier in size. It is also still a very compact lens. I also have 90mm f/2.8 covered by Tamron 35-150, so f/1.8 on 85mm would be a little different than another f/2.8 lens.
Thoughts on Sony 85mm f/1.8 vs Sigma 90mm f/2.8C?
There is no 90mm listed on the B&S forum, so I have time to make this decision.
ramesesthe2nd wrote:
I got Sigma 24mm f/3.5 and Sigma 45mm f/2.8 C. I am thinking about buying the 90mm to complete my super compact kit, but I am not sure if 90mm is the way to go. Sony 85mm f/1.8 is cheaper (used B&S pricing) and faster and not that much heavier in size. It is also still a very compact lens. I also have 90mm f/2.8 covered by Tamron 35-150, so f/1.8 on 85mm would be a little different than another f/2.8 lens.
Thoughts on Sony 85mm f/1.8 vs Sigma 90mm f/2.8C?
There is no 90mm listed on the B&S forum, so I have time to make this decision. ...Show more →
I have owned both and kept the Sigma 90. I have seen some wonderful photographs made with the Sony 85/1.8 published on this forum, especially some beautiful ones in b&w. And, the 1.8 aperture is an advantage. So it is a close call.
But I decided that I preferred the rendering of the Sigma 90. Also, it is surprisingly small, made for traveling.
But a hard choice. If you try either or buy both and sell one, you shouldn't have any trouble selling on the forum.
ramesesthe2nd wrote:
I got Sigma 24mm f/3.5 and Sigma 45mm f/2.8 C. I am thinking about buying the 90mm to complete my super compact kit, but I am not sure if 90mm is the way to go. Sony 85mm f/1.8 is cheaper (used B&S pricing) and faster and not that much heavier in size. It is also still a very compact lens. I also have 90mm f/2.8 covered by Tamron 35-150, so f/1.8 on 85mm would be a little different than another f/2.8 lens.
Thoughts on Sony 85mm f/1.8 vs Sigma 90mm f/2.8C?
There is no 90mm listed on the B&S forum, so I have time to make this decision. ...Show more →
I had the same decision to make and went with the Sony 85/1.8, mainly because of AF inconsistency and inaccuracy with all of the Sigma lenses that I have used, including the 90/2.8 DG DN.
I had a crazy sharp copy of the Sigma 65/2 DG DN Contemporary, and I reviewed the images that I took with that lens closely before deciding on the Sony 85/1.8. Very few were critically focused when using eye AF on my A1 (humans and dogs) even when subject motion was minimal.
This is what I find with so many of the Sigma lenses on my A1. They are beautifully built, sharp, render nicely, have great color balance, and they all have reliably unreliable AF when shooting moving subjects. I never have the same problems with my native Sony lenses. If Sigma could get the AF up to spec, I would own the entire DG DN Contemporary line.
smpetty wrote:
I had the same decision to make and went with the Sony 85/1.8, mainly because of AF inconsistency and inaccuracy with all of the Sigma lenses that I have used, including the 90/2.8 DG DN.
I had a crazy sharp copy of the Sigma 65/2 DG DN Contemporary, and I reviewed the images that I took with that lens closely before deciding on the Sony 85/1.8. Very few were critically focused when using eye AF on my A1 (humans and dogs) even when subject motion was minimal.
This is what I find with so many of the Sigma lenses on my A1. They are beautifully built, sharp, render nicely, have great color balance, and they all have reliably unreliable AF when shooting moving subjects. I never have the same problems with my native Sony lenses. If Sigma could get the AF up to spec, I would own the entire DG DN Contemporary line....Show more →
I had the same issue with the Sigma 65/2 but not the other DG DN lenses. Well, there is a focus issue with the 45/2.8 under phase detect but that's for another reason.
Anybody shooting the 90 on an apsc camera? Thinking of picking it up as a 135 equivalent prime. Or as a small travel lens for my FF kit, but mostly I use apsc for that.
itai195 wrote:
Anybody shooting the 90 on an apsc camera? Thinking of picking it up as a 135 equivalent prime. Or as a small travel lens for my FF kit, but mostly I use apsc for that.
These were two reasons for I bought Sigma 90/2.8 C,but so far I did not have time to use it on APS-C.
, its probably because the center ain't really the center Fred - in all those de-centered copies!
Paired with the 20 and 35 it's a nice add on to make a small kit used on an A7c. 
