John Cantelo
Well-known member
I'll nail my flag to the mast straight off – I'm a birder who's used binoculars for over 50 years, but I'm not an optics nut or engineer. The technicalities of optical design leave me cold and only impinge on my awareness when I look through a product. So I'm prepared to be shot down in flames for my lack of technical nous.
What I do wonder about is what seems to me a fairly recent stress on 'edge to edge sharpness' as an important factor in selecting binoculars. Obviously nobody wants binoculars where sharpness falls off very sharply and the sweet spot is tiny, but I don't see instruments like this on the market. It's usually a matter of 10-15%.
In all my years of using bins I've always centred my optics on the subject of interest so by and large if the outer 10% of the view isn't quite so sharp then it really doesn't matter. What often does matter though, is to have a generous field of view so that I see birds at the periphery of my view or more easily locate and track birds in foliage etc. An instrument with sparkling edge to edge sharpness may seem better than one with a less good view for the outer 10%, but in reality if it has a field of view of, say, 140m, in practical terms I suspect I'd find it less useful than binoculars with a 150m FoV even if only 135m of that view is razor sharp. That extra 10m of view will allow me to detect a bird otherwise unseen and I'll instantly swing my optics round to get that premier view. So is a stress on edge to edge sharpness, particularly without reference to FoV, misleading?
What I do wonder about is what seems to me a fairly recent stress on 'edge to edge sharpness' as an important factor in selecting binoculars. Obviously nobody wants binoculars where sharpness falls off very sharply and the sweet spot is tiny, but I don't see instruments like this on the market. It's usually a matter of 10-15%.
In all my years of using bins I've always centred my optics on the subject of interest so by and large if the outer 10% of the view isn't quite so sharp then it really doesn't matter. What often does matter though, is to have a generous field of view so that I see birds at the periphery of my view or more easily locate and track birds in foliage etc. An instrument with sparkling edge to edge sharpness may seem better than one with a less good view for the outer 10%, but in reality if it has a field of view of, say, 140m, in practical terms I suspect I'd find it less useful than binoculars with a 150m FoV even if only 135m of that view is razor sharp. That extra 10m of view will allow me to detect a bird otherwise unseen and I'll instantly swing my optics round to get that premier view. So is a stress on edge to edge sharpness, particularly without reference to FoV, misleading?