I don't know I can see the edge of the FOV and if it is smeary or fuzzy due to field curvature or whatever, it bothers me. If nobody sees the edge of the FOV why did Swarovski spend so much money on R&D and make such a big deal out of the new flat field sharp edged El's when they came out. Every time I scan, I see the edge of the FOV. IMO, sharp edges and bigger FOV are the biggest advancements to come along in binoculars in years.CAN see, how? I don't believe one can tell whether the edge is entirely sharp while looking at the center. I was just testing that with my EII with a similar FOV: 60-70% out maybe, which is why a large sweet spot is desirable. But the edge, no. You would actually have to look out well away from the center to notice that the edge is a bit soft, which isn't optically ideal anyway, and most bins start to kidneybean when you try. So NLs are perhaps "best" for the birder who insists on doing this, but I'll bet most don't.
And even when momentarily noticed, modest edge softness due to field curvature is easy to forgive, unless you're somehow determined not to. After all, bins have been like that for ages. What can bother me is the level of astigmatism/coma I've seen (Zeiss FL comes to mind) where things start actually to look smeary around the edges. That does distract me, and it's even uglier when panning, so I avoid it.
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