Magnification
Binoculars come with numbers like 7x50, 8x29, 8x40 or 10x50. The first, lower number is the magnification; what you see through them is that many times larger than you would see with bare eyes.
The second number is the diameter of the large front (objective lens) in millimeters. The greater the number the more light is captured. So the largest numbers such as 10x50 mean the highest magnification and with the greatest amount of light let in through the front lenses. Are they best for bird watching, then? Not necessarily, because 1) they are heavier than binoculars with smaller numbers and 2) they magnify movement as well. So they are best used in a stable situation when, for example, you are sitting or have them on a tripod. On the other hand 8x20 binoculars are light and easy to carry but have a smaller field of view and let in the least light.
7x35 or 8x40 is usually recommended for birdwatching. No matter what the price is we always recommend that you always try them out before before buying.
.jpg "Bushnell H2O 10x42 (15-1042)")
