Forgive me if I'm explaining more than you need to know, but...
the first number is the amount of magnification (7x, 8x, 10x). More magnification isn't necessarily better as every shake is also magnified. Most people can't handhold over 10x without the image shake becoming more annoying than they can handle. (Bracing yourself on the trunk of your car or something can help steady things).
The 2nd number is the diameter of the the objective lenses (a 7x35 has 35mm diameter lenses, 10x50 has 50mm diameter lenses). This is more important for night viewing (or astronomy) than daylight viewing, but all things being equal, the bigger the objective lens the "brighter" the scene will appear.
Assuming decent optics, the MOST important thing in binoculars is collimation. If you are buying a used set, make sure that both monoculars are pointing in the same direction. If they aren't you'll see a double image (using both eyes) or a shift in the image when closing one eye and then the other. Walk away from any pair that is not properly collimated. (I'd prefer to buy a pair in a store, over mail order, for this reason.)
Another thing to consider is how weatherproof, shockproof ect. they are. For daytime all-weather use, I like the armor-coated waterproof military Steiner (6x30s) - particularly if you can find them in a pawn shop where they have them priced at $25 like the beat up Bushnells beside them on the shelf. :twisted:
Darren Addy
Kearney, NE