I'm baffled, seriously. What else are the MTF charts there for?
To know about a specific lens - sensor - converter cmbination. I'm aware that with your prehistoric RAW converter from 2011 and my C1 10 and soon 11 from these days, the results already will be different. And you two guys keep on with your sermon that we readers cannot cross compare lenses - which is a fact. But we also cannot tell about a lens (some even without optical rating, others with rating - alone that is not very useful if you look at some Canon 5D "R" tests) which performs well at 21 MP how it will behave at around 50 MP. So, to me the MTF numbers are only telling something within a system, but fail as an absolute scale. Which is what lenscore
provides provided (their last test was from months ago)
And what does this rating tell you if you want to know how the lens performs on a sensor that is very different?
Telling me? Nothing of relevance. To my own decisions your ratings do not matter. Your findings and charts do matter, but the rest... And what also does matter - and I repeat myself because you two testers don't care much about USB docks and consequently the improvements these docks can give the lens in cooperation with a certain AF module - is the possible customization of DSLR lenses which no first party DSLR manufacturer has to offer.
I'm not sure why you keep coming back to this single point. Each lens is tested and judged across the whole specification set it offers. The Nikkor starts at f/2.8, and it is fairly great at its largest aperture already.
I come back to this point because either there is a comparable rating system with transparent rules or two guys are throwing in some decorative stars I'm fine with both. Please don't feel offended but when I'm researching about a lens, PZ/OL is only one address and not the most important to me.
The Sigma starts with a bigger aperture, and thus is rated across a larger aperture range. At f/1.8, it shows weaknesses at the borders and corners. Which, by the way, I think can even be seen in the full res sample you posted (the lady at the lake). I don't find the border anyhow impressive in there and think they match the findings quite well.
The lady was out of focus (although not willingly) the walls opposite the river are sharper in my memory. I understand your remark that way that wide open lenses will always have a handicap compared to less wide open lenses. This is one disadvantage of this kind of rating: Most wide open lenses perform as well or better at f/2.8 or f/4. The slow lenses cannot be faster, but the wide open ones can be stopped down. Therefore a comparison works between wide open OR less wide open, but not a wide open compared to a less open one. You rated the Nikkor on a 24 MP camera - I see the pictures with 45 MP and am surprised about sharp borders. Wide open, that is. This weekend - if the weather allows it - I can compare both lenses on the same camera. Maybe I'm wrong, and the Nikkor is still better, but at the moment it looks the other way.
If a lens offers a large aperture, we expect it to be great across the frame at that setting to receive a great rating,, when it comes to MTF, it's as simple as that.
Rubbish. At least speaking of an ultra wide angle lens, just show me a single picture where you take a picture of something with a perfectly flat focus area which needs to be sharp across the frame - test charts are an exception, no real life If you need sharpness across the frame you also need best ISO, lowest vibration and a possibility to adjust the frame carefully. That all points towards a good tripod and then it doesn't matter to stop down for max resolution.
Beside: looking at the available data, I still have doubts the Sigma matches the Nikkor at 14/2.8
And I cannot or will not say it matches unless I can prove it. But if I can prove it, the next beer is on you.