Sigma 20/1.4 vs Loxia 21 by Ming Thein

[Sid]

http://blog.mingthein.com/2015/11/23/sigma-20-art-vs-zeiss-21-loxia/

Summary:

In hindsight, I think ‘battle’ may have been the wrong term to use: it really isn’t one. What we have are two of the best wide angle lenses I’ve yet seen, period. Both have tradeoffs ut they’re sensible; there is therefore no clear winner here – you may value the 21 Loxia’s size over the Sigma’s speed, or autofocus over the ability to take filters. Or field curvature over corner resolution – etc. Despite being similar in focal length, the 21 Loxia and 20 Art are an excellent example of where lenses are clearly built for very different application profiles – and still capable of achieving the same high standard of performance. There are situations in which I strongly prefer the Loxia over the Sigma, and vice versa – fortunately, these almost never overlap. For the first time in a comparison, my choice here is actually very simple: I have reasons enough to have both. MT

What do people think? If you're a Sony FE user what would your choice be? I'm interested in using a lens at this focal length for astrophotography and since I hike to most of my spots, I'm wondering whether the 2 stops can effectively be compensated for by stacking/high ISO... So many compromises

 

[rich_]

If i owned an FE mount camera then i'd go for the Loxia. I owned the Zeiss 21 ZM Distagon for my camera previously and it was a fantastic lens.
I also found at that focal length there are very few occasions where you will actually require f1.4, besides taking photos of coffee cups with blurry backgrounds. You can hand hold at a slower shutter speed and the ISO ability of the Sony cameras can cover the extra stops.

I happily used a 21mm 2.8 with a max ISO of 1600 and barely ever needed more light. I however wasn't shooting sport (who does with a manual focus lens) or things which required a very high shutter speed.

I'd be happy with the Sigma for my SLR, but it's a bit of a heavy monster!

 

[Sid]

I was thinking of the extra speed primarily for astrophotography because, apart from that, I'd only really need f/4 and above at that focal length. The Sigma also does have the advantage of price (roughly 1/2) and autofocus which if anything like the other Art lenses will be excellent on an a7R II.

Out of interest, were you using the 21 ZM on an FE body? Or was it on a Leica?

 

[rich_]

Oh sorry, I didn't see the price of the Sigma, If it was half the price then i guess I'd probably go with the Sigma assuming the bulk wasn't too frustrating! I used the ZM on a M9 Leica. I'm not sure whether it brings on Magenta corners on Sonys but if otherwise its a great lens which is very light!