Bushnell Powerview 20x50
Bushnell Powerview 20x50 is part of the Powerview series which is the entry level series from Bushnell; the viewers are made in a variety of lens combinations and have a sharp price/quality ratio. The coatings of the glass are, depending on the type, multi-coated or fully multi-coated. The lens coatings are designed to guide the light captured by the lens to the eye in an optimum and efficient way. On the outside, almost all models have an extra rubber grip layer so you have (and keep) everything completely under control! In the middle is a convenient and easy to handle focus knob to get the sharpest view of your target. The viewers are provided with fold-down eyecups so you can use the Bushnell Powerview 20x50 in no time even wearing glasses.
If an object is farther away it is wise to choose a high magnification. The advantage of a high magnification is that the image is much closer, so ideal for use on open plains. Think of the coast or vast fields of grass and heather.
The twilight factor is calculated by multiplying the lens diameter and magnification after which the square root of this is taken (is indicated in our specifications). If you sit in densely forested areas, or want to see animals that only appear at dusk (e.g. deer) it is wise to go for a viewer with a twilight factor of at least 15 (preferably higher). The twilight factor is also influenced by the coatings on the lens, the type of glass used and the coatings on the prisms. More expensive binoculars may have a lower twilight factor but usually yield a much brighter picture than cheaper binoculars with a higher twilight factor do.
Weight and dimensions
If you travel or go hiking a lot then compact binoculars are recommended. These are easy to carry and not so heavy on the neck. However, a compact viewer has a smaller lens and therefore a lower twilight factor. Also, the field of view is smaller when you go for a high magnification (higher than 9x).
Porro or roof prism viewer?
The Powerview series is available as porro binoculars and roof prism binoculars. Porro binoculars (see diagram below) are broader binoculars and based on the first design of binoculars. The Porro consists of two rectangular prisms attached together so that the light is reflected three times, resulting in a correct image. The conventional binoculars use Porro Prisms.
A roof prism viewer uses a roof prism (see diagram below). This design is technically more complicated than a Porro prism design, as it uses prisms which must have very accurately polished edges. The light is reflected four times. This design is more compact, but because the path of light is longer and the prisms more complicated, the quality of the glass and the manufacturing must be higher than that of the Porro Prism design. Only then can an equal performance be achieved. Roof Prism binoculars have straight tubes as shown in the picture.