[Rover]

Just when I got around to buying the L...

http://www.dpreview.com/articles/5116211...m-art-lens

[Brightcolours]

This lens seems to have had the shortest life cycle in history:

"THIS PRODUCT IS DISCONTINUED."

http://www.sigmaphoto.com/product/24mm-f14-dg-hsm-a

:lol:

[Rover]

All right, joker, whatever the fluke was, now it's fixed. The page says COMING SOON. 

[Scythels]

'Lots' of spherical aberration in this one.  It'll look a bit fuzzy on the 20mp sensors wide open and very fuzzy on the new 50mp beast.

 

Astigmatism is respectably low though.

[JJ_SO]

All right, joker, whatever the fluke was, now it's fixed. The page says COMING SOON. 

I learnt, this means something like "probably within this century, on Tuesday"

 

But besides of that, more interesting to me is a DP0 quattro with 14mm lens  :blink: with 0.5% distortion at infinity (wow) and a Conversion Lens for Sigma dp3 Quattro as well as a Arca-compatible collar-foot for 150-600 Sports (I haven't give up on that).

 

And the best of all: I can just make a longterm investment and in about 2, 3 years… alright, enough joking, otherwise I need to continue with something like "when the 24 Art becomes available, we might see some test results of the 50 Art here at PZ"  ^_^

[youpii]

'Lots' of spherical aberration in this one.  It'll look a bit fuzzy on the 20mp sensors wide open and very fuzzy on the new 50mp beast.

 

Astigmatism is respectably low though.

How do you know?

[Scythels]

I can tell based on the MTF chart.  Maybe I should save the particulars for the future but for a centered system the only non chromatic aberration permitted on the optical axis is spherical aberration.  Based on the implied slope between 10 and 30lp/mm at the leftmost position on the graph I can tell with some degree of accuracy the quantity of spherical aberration in the system. 

 

The 'bumps' in any one image plane (i.e sagittal or meridonal) are shifts in the balance of the aberrations.  A system without an asphere that has a "nice" design free of pupil aberrations will smoothly degrade towards the corners and maybe experience a local min and then rise in performance again thanks to vignetting.  I am ignoring them and assuming they are fluctuations in the higher order spherical aberration.  The lower order coma and higher order spherical continue to degrade performance towards the edges until about the 20mm position where the meridonal plane drops off a cliff - this is most likely higher order coma and the "net" is strong astigmatism, but in general the resolution in the meridonal and sagittal planes remains quite similar so astigmatism is okay.

 

I'll save more for the future =)

[JJ_SO]

Scythels, maybe you care for a side look to the competition?

 

The Sigma doesn't look too bad, does it?

 

Source: DPreview Forum

[Scythels]

When I said 'lots' in quotes it really was because the level of spherical aberration is not too high.  The astigmatism is much stronger with sigma's lens than with canon's which leads me to believe the sagittal and tangential fields bend in opposite directions which will hamper the performance as the lens is stopped down, but the sigma's performance looks quite good wide open and I would expect very good results stopped down regardless due to the very deep DoF.  The limiting aberration is just primarily higher order spherical aberration i.e a similar aberration characteristic to samyang's 24/1.4, but better correction on the whole.

[JJ_SO]

The reason to buy a fast wide angle is to need it wide open - and for that the Sigma looks slightly more promising than the others. Not matter how much aberration in total the Sigma delivers: the competition will get problems to sell their steeply priced glass. Again, good to have choices. I just don't see it as such an improvement that I'd "need" to sell the Nikon, but who knows?