Originally Posted by Binastro
Hi 18000 bhp,
Is the sweet spot so small because of field curvature?
Does the sweet spot increase if one focuses a bit off centre?
Perhaps my eyes are a bad match for field flattener lenses--something I hadn't previously considered. Next time I am in a Cabelas maybe I'll look through the Zeiss Victory (or another field flattener bino) and see if I have similar perceptions.
If I go a bit off center I get blur and it can't be focused. Once I go 10-20% toward the edge below center horizontal I get extreme blur worse than the $100 binos I have access to. Above horizontal is better as I can probably get 40% to edge before it gets bad. Based on reviews I wasn't expecting or desiring edge-to-edge sharpness but these are really limiting.
My left eye perceives a similar sized sweet spot as the right but the blurring is significantly worse even when I hold the binos are upside down.
Anyways, these things really are fantastic as long as I stay on task and keep my subject just above center.