Hi Jack,
Here's an example of where the 50 f/1.2 Ai falls down a bit compared to the Noct. Admittedly the stars are elongated a bit due to the length of the exposure, but the coma & flare around the bright stars is obvious. While I don't have a Noct, I'm certain it would perform much better on this subject.
And this is with a crop sensor. A full frame camera would show even more coma near the edges of the field.
Hi.
It's very difficult to rate that photo as I don't know the conditions under which it was taken, nor is there a juxtaposition provided as a measuring stick.
Any lens can take a bad image under bad conditions.
That said, according to Ken Rockwell, some astrophysicist bought like 5 Nocts for that purpose specifically. So I am sure (for certain specific uses) the Noct MUST provide certain key advantages.
Still, does that make a used 58mm f/1.2 Noct worth
5x the price of a brand new 50mm f/1.2 Ai-s?
Also, does the Noct provide **any** advantage over the 50mm Ai-S in
standard lighting?
I don't shoot astronomy; I shoot in optimal light. (Or try to.)
I am pretty convinced that, in optimal light, the 50mm Ai-S can do
anything the Noct can do,
anything, for $700 rather than $3,500.
If someone wants to spend an additional $2,800 to remove the coma from astronomy images, that is their choice. But they would have to be heavy into that kind of shooting.
With that said, I will probably buy a Noct at some point, just to take it for a spin, and make/record the differences it makes myself (if any).
But I think, for the most part, the "difference" between the Noct and the Ai-S in normal-light shooting is more myth than reality ... essentially nothing worth talking about ... in all but the most extreme conditions.