I have to wonder why the popular compact roofs are either 8x20 or 10x25 or thereabouts? Is there some optical design limitation why they can't offer, say, a 7x25, or maybe a 6x20? It seems like lowering the magnification on these tiny bins would make them much more user friendly? Am I missing something obvious? Just wondering out loud. If I could buy a 7x25 Ultravid I'd jump all over it.
Dan C
[QUOTE=highxj]I have to wonder why the popular compact roofs are either 8x20 or 10x25 or thereabouts? Is there some optical design limitation why they can't offer, say, a 7x25, or maybe a 6x20? It seems like lowering the magnification on these tiny bins would make them much more user friendly? Am I missing something obvious? Just wondering out loud. If I could buy a 7x25 Ultravid I'd jump all over it.
Dan C[/QUOTE]
There is no optical design limitation. Power is determined by the focal length of the eyepiece. With everything else equal, a 7x would have a wider field of view and a bit more eye relief than an 8x25.
There seems to be a "power prejudice" amongst many birders. 8x, for some reason, is considered the minimum for most birding binoculars. I would agree that for medium and full-sized binoculars, 8x is a very versitile magnification, and one that is usually recommended if you only have one binocular. But in compact design, so many features are comprimised by the size, that lowering the power would improve a compact's usefulness, in my opinion.
BTW, many experienced birders prefer the 7x even in full-sized binoculars. They like the increased light gathering capability, the inherently wider field of view, and the steadiness that less power provides.
Someone in a recent thread pointed out that Swarovski sold ten times more 8x30 SLC binoculars than 7x30 SLC. These guys are in business to make money.
(The B&L Custom Compact 7x26 (a reverse-porro) was for a great many years considered to be the only compact binocular useful for full-time birding. I own the Custom Compacts, and I used to own the Nikon LG L 8x20. The Nikon's were better on sheer optics, but not as useful for full-time birding, for me anyway.)