Considerations of Size and Weight can be challenging but are important considerations. Compact binoculars offer smaller size and weight advantages, while full sized have greater light gathering capability but are heavier. To enhance light transmission through a binocular, manufactures apply a microscopic film of magnesium fluoride either to the prism, lens or both. This microscopic film diminishes the reflected or stray light inside a binocular allowing more light to be transmitted to the users eye. The more applications of this coating, the greater the reduction in glare and reflections producing a brighter crisper image.
More coatings mean brighter, crisper images.
An optic with 6.5 degrees of angle can be calculated by multiplying 52.36 feet. Field of view will decrease when magnification is increased. Binoculars made for eyeglass wearers should offer a minimum of 18mm of eye relief. Eyeglass wearers should seek a binocular with a minimum of 18mm of eye relief. More is better.