Setting the dioptre for your binoculars: It is crucially important that you set up your binoculars for your eyesight. We have included the handy instructional video on the right and written instructions below.
1. Please refer to the manual which came with your binoculars to determine where the dioptre is located. It is usually on the centre focus knob or on the right-hand eyepiece.
2. Pick up your binoculars and look through them as you normally would.
3. Close your right eye, so that you are only looking through the binoculars with your left eye.
4. Pick an object that has texture about 10 metres away and, looking through your left eye only, turn the centre focus wheel until the object is sharp and in focus.
5. Keeping your binoculars pointed at the same object, then close your left eye and open your right eye.
6. Using the dioptre - and only looking at the object through the right lens with your right eye - turn the dioptre until the object is sharp and in focus for your right eye.
6. Lock the dioptre back into place on that setting. The binoculars are now set up for your eyes and, from now on, only focus the binoculars using the centre focus wheel.
Technical talk: what all the numbers and names mean.
⊙ Magnification (Power): Binoculars are often referred to by two numbers separated by an "x". For example, 10x42. The first number is the power of magnification of the binoculars. With 10x42 binoculars, the image of the subject being viewed is brought ten times closer to you through your binoculars (compared to viewing the subject with the naked eye). In our experience, we have found that a magnification of 10x is ideal for safaris. 8x magnification would do but we feel that, unless you have a specific reason for using 8x magnification binoculars (for example, if you are a birder heading to the forests of Uganda), it is always better to have the subject you are viewing 10 times closer. We also feel that at 10 times magnification lens shake does not come into play for the vast majority of people.
⊙ Objective Lens Size (aperture): The second number in the formula (10x42) is the diameter of the objective front lens, measured in millimeters. The larger the objective lens, the more light that enters the binoculars and the brighter the image. In our experience, we have found that an objective lens size (aperture) of 42mm is the ideal for safaris to allow for as bright an image as possible in low lighting conditions.
⊙ Roof Prism System: In roof prism binoculars, the prisms overlap closely, allowing the objective lenses to line up directly with the eyepiece. The result is a slim, streamlined shape in which the lenses and prisms are in a straight line. Roof prism binoculars are less bulky and more rugged than an equivalent porro model.
⊙ Field-of-View (F.O.V.): The side-to-side measurement of the circular viewing field or subject area. It is defined by the width in feet or metres of the area visible at 1000 yards or meters. A wide-angle binocular features a wide field-of-view and is better for following action. Generally, the higher the magnification, the narrower the field-of-view.
⊙ Eye Relief: The distance a binocular can be held away from the eye and still present the full field-of-view. Extended or long eye relief reduces eyestrain and is ideal for eyeglass wearers.
⊙ Diopter Adjustment: A "fine focus" adjustment ring usually provided around one eyepiece to accommodate for vision differences between the right and left eyes.
⊙ Waterproof/fog-proof: Some binoculars are O-ring sealed and nitrogen-purged for total waterproof and fog-proof protection. These models can withstand complete immersion in water and stay dry inside. The interior optical surfaces won't fog due to rapid temperature change or humidity.