Increased magnification = increased woble, so for hand-held use a magnification of  8x to10x is usually sufficient.  With binoculars of a higher magnification a tripod is advisable.

Field of view is expressed by either width of panoramic view  at a distance of 1000 meters or in degrees.  The higher the figure the larger the field of view.

Objective size   (OG)  The larger the objective, the higher the light transmission. A 50mm objective will allow 2-3x the light transmission of a 30mm objective. The amount of light hitting your eye is known as exit pupil diameter (EPD). To calculate the EPD, divide the objective of the binocular by the magnification eg: 7 x 50 = 7.1mm  exit pupil diameter (EPD)