BC, you also can imagine - like me - the radius or at least the shape of the "in-focus-field" can change depending of the distance?
I imagine a relief which changes between close and far distance it's levels.
Therefore there might be field curvature at testing distance, but a very different one at infinity. Speaking of infinity: Stars are not arranged in a focal pane... question just remains if in the curvature focus at infinity is possible or not.
Quote:If I need sharp borders. I'll stop dwon anyway, but I really want to know a single case or subjectwhen you need high res corners wide open? In my book there's none of this subjects.Not even in theory.
"Theory?" - that's my keyword, right? 
Seriously: if you compose your images following the rule of thirds or golden rule, then your main subject is close to or (if you stretch the rule a little) almost at where we measure border performance. In any case closer to border than to the center.
Quote:Edit: Oh and by the very way: The Nikon got 4 stars at it's time. At 14 mm and f/2.8, it is in no respect better than the Sigma - not on 20 and especially not on 45 MP!
Besides the fact that we keep preaching "thou shalt not compare results across systems": are we looking at the same reviews? The Nikkor has excellent borders at f/2.8 already (on the D3x... on the D850, we will hopefully see in not too distant future).
It got "only" 4 stars because of the flare issue, otherwise the rating would have been a little higher.
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PZ's sharpening definitely muddies the waters, trying to compare the 5DS-R and D3X results. And Lenstip's reviews do not clear things up a little, as the Nikkor 14-24mm f2.8 appears to be only tested on a D200?
So will have to wait till the Sigma 14mm f1.8 is tested on a D3X.
And yes JoJu, I agree with the distance appears to have a big influence on the shape of the focus field, demonstrably so with certain lenses.
Quote: If I need sharp borders. I'll stop down anyway, but I really want to know a single case or subject when you need high res corners wide open? In my book there's none of these subjects.Not even in theory.
Strange JoJu you forgot the star-spangled night sky .........in practice and theory!
......the very reason I bought the Samyang 14mm.
11-21-2017, 03:51 PM
(This post was last modified: 11-21-2017, 04:13 PM by mst.)
Markus,
I simply don't believe that the Nikkor @14mm and f/2.8 will be better in any aspect than the Sigma 14mm and f/2.8. Distortion is roughly the same - mind you, I'm talking about f/2.8. I think the Sigma will kick Nikkor's ass in any possible way.
But it got 4 stars - and the Sigma only 2 1/2 respectively 3 1/2. I already am a bit suspicious because at 21 MP the extreme borders are better and at 50 MP weaker - I don't think,. one can blame "field curvature" here?
Don't get me wrong, I don't want to lift up the rating of the Sigma. I just think, controlling the flares much better, offering 1 1/2 stop more light, being at least as sharp in the center as the Nikon wide open (not to speak about stopped down to f/2.8) this rating is a bit off my experience with the lens.
Anyway.
Oh, and tehre's a remark of a reader about "Available in native Canon and Nikon mount, it is possible to use Sigma's Mount Converter MC-11 for using the lens on Sony and Sigma mirrorless cameras."
I think the reader's right to criticize that part of the text.
MC11 is either to convert a Canon or Sigma lens mount to connect to a Sony E-mount. You cannot use the MC-11 to connect a Sigma lens mount on a Canon camera. Of course, who ever will use this brick with a Sigma camera, but you never know....
Markus,
I simply don't believe that the Nikkor @14mm and f/2.8 will be better in any aspect than the Sigma 14mm and f/2.8. Distortion is roughly the same - mind you, I'm talking about f/2.8. I think the Sigma will kick Nikkor's ass in any possible way.
But it got 4 stars - and the Sigma only 2 1/2 respectively 3 1/2. I already am a bit suspicious because at 21 MP the extreme borders are better and at 50 MP weaker - I don't think,. one can blame "field curvature" here?
Don't get me wrong, I don't want to lift up the rating of the Sigma. I just think, controlling the flares much better, offering 1 1/2 stop more light, being at least as sharp in the center as the Nikon wide open (not to speak about stopped down to f/2.8) this rating is a bit off my experience with the lens.
Anyway.
Oh, and tehre's a remark of a reader about "Available in native Canon and Nikon mount, it is possible to use Sigma's Mount Converter MC-11 for using the lens on Sony and Sigma mirrorless cameras."
I think the reader's right to criticize that part of the text.
MC11 is either to convert a Canon or Sigma lens mount to connect to a Sony E-mount. You cannot use the MC-11 to connect a Sigma lens mount on a Canon camera. Of course, who ever will use this brick with a Sigma camera, but you never know....
@Joju - how would you rate the Sigma based on these charts?
Honestly I was about to go lower just based on the MTFs but I thought that the bokeh is too nice for that.
I can add a "field" rating here - which is probably more like 3.5-4*.
Klaus, I don't know, honestly. On one hand it's consistent to base the ratings on MTFs. On the other hand the lens can do some tricks others can't, at least according to the shots I made with it so far.
I don't think it's 1 ½ ★ worse than the Nikon. The Canon 11-24/4(!) got "no rating at this stage". Meanwhile the Sigma "at this stage" got a rating at 50MP and if you check the MTF, the corners of the Canon at 14/4 are worse, the center and borders slightly better and no MTF at close center. Hmm.
Do what you like as a rating, it's no problem for me to keep the feeling this rating is not doing justice to a lens like that - I have no better suggestion. And besides of any ratings, the lens works the way I was hoping for - I am not Sigma, I can enjoy a "badly" rated lens without being afraid about bad sales. 
It is due to it's weight and size anyway no lens one just throws in the photo bag. It is highly debatable if an UWA zoom like the Nikkor or the Canon, even the Sigma 12-24/4 is not a better idea at the end, all are "more versatile". I bought it for low light and for bokeh at closer distances with more background than usual - there's no real alternative to it, but I also don't find it perfect. For landscapes in sunlight I'd prefer it to the Nikkor. For architectural "inside a room" views the Nikkor offers a better package.
But you see, there's a lot more than just MTFs which (might) matter for people interested in it. I think, the best recommendation is "rent one and see if it works for you".
11-22-2017, 07:27 AM
(This post was last modified: 11-22-2017, 07:31 AM by Brightcolours.)
It again is clear (to me at least) that the way you guys approach the MFT tests with the sharpening makes for problematic results that no one really can evaluate.
The sharpening exaggerates sharpness, and will not touch less sharp results, exaggerating the difference in corners and center, and also skewing results twice when comparing for instance how that Nikkor 14-24mm f2.8 did on 24mp.
I also wonder if the R-ness of the 5DS-R also brings its own part of the problem, here. Fake sharpness from "no" AA-filter skewing results up until the lens acts as AA-filter (corners).
Something worth investigating?
The 50mp versus 21mp results do show part of the sharpening issue(s). The 50mp extreme corners getting lower results than the 21mp extreme corners.
M TF. Multilateral Trading Facility. Modulation transmission frequency. So "MTF" without "charts" makes as much sense as "gimme a 17er" without "wrench". People understand fi someone lying under a car yells that in a workshop.
M FT is abused for µ 4/3. 
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