[JJ_SO]

Is the field curvature constant at all distances or does it change during various distance settings? Asking in general. With it's 4 aspherical lenses it's a challenge to design anyway.

 

When the sky will become a bit clearer, I like to verify how much of an influence this flaw has. To me it's better than your rating, but I have different prioirities.

[Klaus]

I don't think that the flaws will be noticeable in real life in the vast majority of use cases. The performance is pretty good at medium apertures and, as you noted, it not that relevant in shallow DoF scenes. The results are, obviously, also much better at 21mp. 50mp is simply a killer.

[JJ_SO]

45 MP is not much less, but I was a bit surprised the corner weakness was relativley low at the shot with the woman at the river - and that shot was taken at f/1.8...

[toni-a]

It's not about the lens, but could you compare 50MP pictures downsampled to 21 MP versus native 21 MP ?

[Rover]

I don't think many people are going to use 5DSR for astro, as this camera has (relatively) low top ISO anyway.

Besides, it eats through lenses like a Langolier.

[Klaus]

I don't think many people are going to use 5DSR for astro, as this camera has (relatively) low top ISO anyway.

Besides, it eats through lenses like a Langolier.

 

Fully agreed. The Sony A7S II should be awesome for this ... if it wasn't for its star eater issue ;-)

[Brightcolours]

Field curvature certainly does not have to be the same at different focus distances.

 

Case in point:

http://forum.opticallimits.com/index.php...-f2/page-2

 

Hence,  the Sigma showing noticable field curvature at testing distance, but less or no noticable field curvature at infinity is a possibility.

[Klaus]

Well, the field curvature is somewhat eaten by the increased DoF towards infinity.

But again let's be fair - 3-4 years ago, the Sigma would have been cheered regarding its performance.

I'm pretty much convinced that the D850 will produce similar figures. Most Sony FE lenses have also issues on the A7R II.

[JJ_SO]

Well, the field curvature is somewhat eaten by the increased DoF towards infinity.

But again let's be fair - 3-4 years ago, the Sigma would have been cheered regarding its performance.

I'm pretty much convinced that the D850 will produce similar figures. Most Sony FE lenses have also issues on the A7R II.

 

If 3-4 years ago Sigma would have been cheered, then who's cheered today?  Maybe it's just me, but I'm not aware of any other 14 mm lens with that quite high center and close center performance. 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.

 

Okay, once I used the Zeiss 12 mm on the Fuji to get some shots in an exhibition just with less reflections.

 

This one can do with a Fuji, with a 2.5 kg FF combination the guards usually jump quickly - but even for this purpose - no reproductions but some memories - that lens will do just fine, as most pictures/paintinings are lit sufficienty to view them.

 

I want to know, Klaus, when you need high res corners wide open. To me, your verdict appears not realistic and at the same time you did say only one single word ("It's not a wonder lens in terms of flare/glare but that applies to many lenses in this class anyway.") about flares - these matter more and compared to the Nikon 14-24, that Sigma IS a wonder lens (most others are so, too  ^_^ ).

 

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!

[Brightcolours]

It is not just that increased DOF masks field curvature, field curvature can be gone or worse at different focus distances (see the images from the UMN 55mm f2 in link above for a clear example, for e lens which does not even have moving elements). I do not know how to test that reliably, and obviously I do not have that lens even if I did. 

 

Other issues also can vary depending on focus distance with lenses, like bokeh character, astigmatism.