| CHOOSING THE RIGHT BINOCULAR: |
MAGNIFICATION
Normally expressed as 8x (eight times), 10x or 12x, this gives an indication of how much larger your subject will appear when compared to normal eyesight. As this will probably be the most important factor in choosing your binoculars, it should be noted that higher magnifications not only bring your subject closer, they also emphasise any shake or wobble as you hold them. |
OBJECTIVE DIAMETER
This is the measurement in mm. across the front lens element and gives an idea of the light gathering power. In general terms, the larger this number, the brighter the image. This number is placed after the magnification in a binocular’s description, so a pair of 8x26 binoculars gives 8 times magnification and have 26mm diameter front elements. |
MINIMUM FOCUS
A measurement of how close you can get to your subject and still keep it in focus. |
FIELD OF VIEW
Measured in degrees, this tells you the angle of a scene that you will be able to see. The larger this number, the wider the angle. |
RELATIVE BRIGHTNESS
A number which can be used to compare the apparent brightness of different binoculars, it is calculated by squaring the exit pupil size. If you want to use your binoculars in low light conditions you should ensure that they have a high relative brightness. |
EXIT PUPIL
This is a measurement of the bright circle which can be seen in the eyepiece when holding a pair of binoculars at arm’s length. It is calculated by dividing the objective diameter by the magnification. As the human eye varies between 2mm and 7mm, it is important to choose binoculars which have exit pupils between these figures |
