Sigma 14mm f/1.8 Art @ LensTip

ahsanford said:
natek said:
I just grabbed myself a copy. Any tests you guys would like to see? Hoping for a clear night to get at least some test shots. Anything else?

Regards,
Nate

Um, let's see:

  • Coma
  • Have another look at coma
  • Vignetting
  • Check coma again

- A

P.S. Don't listen to me too seriously. I don't shoot astro -- I'm just parrot-ing why every superfast ultrawide has failed to meet astro shooters' (very very high) expectations the last few years: coma usually underwhelms.

It does make me wonder - how hard is it to control coma? Are the lens designers unaware of the thirst for coma improvements, or as with other things is it a tiny-but-vocal minority? Is it really expensive to control coma? Is it even possible to avoid it in fast UWA designs (has anyone done it yet)?

The sequence I've seen, over the years, of hope and disappointment with every single announcement and review of a new fast UWA has made those questions simmer in me for a while. They're serious questions, by the way, if anyone knows the answers - I really just don't, but the repetition of the cycle is fascinating.
 
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LonelyBoy said:
ahsanford said:
natek said:
I just grabbed myself a copy. Any tests you guys would like to see? Hoping for a clear night to get at least some test shots. Anything else?

Regards,
Nate

Um, let's see:

  • Coma
  • Have another look at coma
  • Vignetting
  • Check coma again

- A

P.S. Don't listen to me too seriously. I don't shoot astro -- I'm just parrot-ing why every superfast ultrawide has failed to meet astro shooters' (very very high) expectations the last few years: coma usually underwhelms.

It does make me wonder - how hard is it to control coma? Are the lens designers unaware of the thirst for coma improvements, or as with other things is it a tiny-but-vocal minority? Is it really expensive to control coma? Is it even possible to avoid it in fast UWA designs (has anyone done it yet)?

The sequence I've seen, over the years, of hope and disappointment with every single announcement and review of a new fast UWA has made those questions simmer in me for a while. They're serious questions, by the way, if anyone knows the answers - I really just don't, but the repetition of the cycle is fascinating.

i am no expert at this but i think it is just an inherent issue with UWA as coma as i understand is caused by light rays coming from an off-axis point of light compared to image plane (thank you google) as one could imagine be very difficult to correct in an UWA lens

what i think a lot of people gets mixed up tho (including me up until recently) is coma vs astigmatism, coma is where you get the comet tail effect whereas astigmatism is where you get the cross/bat wing looking effect

imho while coma and astigmatism is definitely present in the sigma 14 art it really only happens towards the extreme corners and i don't think practically speaking it affects the overall image much, i think sigma has done a great job overall with designing this lens

Milky Way over Glass House Mountains by Tony, on Flickr

edit: i had a look at TDP's review and feels my copy performs a little better in regards to astigmatism side of things...guess there is always going to be your copy to copy variation as well

edit 2: this is a seriously capable lens

First attempt at interior/real estate by Tony, on Flickr
 
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