An all purpose magnifying optical device should have a MINIMUM of 5 times the multiplication rate for the size of the objective lens. (this is the single most important feature)
What this means is that a pair of 7x35 binoculars will collect light at the same rate your eye will where a pair of 7x22 will collect less light than your eye does. Using the rule of 5 here is the first thing to look for:
7x35, 8x40, 9x45, 10x50 and so on. If you get 8x50 that is better than the 8x40 because they will work better in low light conditions.
Coated lenses are an added benefit because the coatings cut down on the losses of the light that you can see. All devices that are not toys have coated lenses - that is why you are told to clean them with a special cleaner and a special cloth. Normal glass cleaner will remove the coatings and even soft cotton cloth can scratch the coatings. Removing the coatings will allow more UV and IR through the optics which will diminish the transfer of the light that you can see.
Now - that objective lens size. You already know that the bigger that lens is, the more light it lets in but it also increases your field of view IF it is larger than 50. The field of view of the human eye is extremely close to that of a 50mm lens with a "standard focal length" The longer the focal length the smaller your field of view. Most optical devices have a very long focal length to prevent the "fish eye" effect. so, again, if you want a larger field of view you need a larger objective lens and a short focal length - as long as you don't get the "fish eye" effect.
Unless you have exactly the same vision in both eyes (very rare) you will want a separate focus lens on one of the two lenses on your binoculars. That way you can get perfect focus in both eyes. On the note of focus You want a mechanical focus screw that does not deflect the alignment of the lenses as they are focused. Cheaper binoculars can be discovered by backing the lenses away from the objective lens as far as they will go and then try to gently move the eye pieces up and down - if they move easily then walk away. Those lenses have to stay in alignment at all times.
Stay away from magnifications above 10 unless you have a tripod - you are better off with a telescope for higher powers of magnification.
That should make your choices fairly bewildering so here are some easy recommendations.
Bushnell 8x50, Nikon 8x50 - 10x50 and 10 x 60, Zeiss 8x50
Now there is a wide choice of prices above, the least expensive is the Bushnell and the most expensive is the Zeiss.
Look around and check out different makers staying with 8 power and 50 mm objective lens to compare. When you find a pair that is crystal clear and close to the top of your price range get online and find the best price.
I bought my Bushnell 8x50 new for less than $50. That was a while back but they are a good pair of binoculars and still work fine.
04-07-2015, 06:54 PM
I have a pair of "Nikon Action" 8x50s. They are sharp, low in weight even though they are large, and armored. They are excellent for birding, and light astronomy. I've seen them 'used' on ebay for less that $30.00.
Great post Paul. I have a pair of Nikon Action EX 7x35 that I keep in my truck and use them all the time. I have some cabelas gift cards to use and I have been thinging of either getting another pair of the same or maybe a higher magnification to leave at the house. The size of the 7x35's is nice in the truck as they aren't too huge and don't take up lots of space.