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Category Archives: BINOCULAR BASICS
Binocular Basics index
Adjustable eyepiece Aperture Armoring of binoculars Bak-4 BK-7 Basic design of binoculars Brightness of image in dim light Central focusing mechanism Central focusing wheel Central focusing knob Central focusing toggle Close focus Coating of lenses Collimation Depth of field Diopter … Continue reading
Image brightness in dim light
Three factors determine the brightness of the image in dim light: The quality of optical coatings, a factor determined by the size of the exit pupil and finally a factor determined by the objective lens size and magnification. Lens coatings: … Continue reading
Depth of field
The “depth of field” of a binocular refers to its ability to keep objects further towards the background and closer towards the foreground in focus without you having to adjust the focus. Stated in another way: Once you’ve focused on an … Continue reading
Focus speed
If you need the binoculars for watching wild animals, in particular birds, the speed of focus is important. While following a bird in flight, you need to change the focus all the time if the bird gets closer or further, … Continue reading
Close focus
Focusing at a distance is no problem for any pair of binoculars; focusing at close range, however, is a totally different matter. This is important, since sometimes you will be in a situation where close focus is important, in particular … Continue reading
Field of view
Another set of technical detail which is imprinted on the binoculars, could be something like this: 367 ft. at 1000 yds. This is the field of view (FOV), the width of the view at the particular distance. In this case … Continue reading
Coating of lenses
Not all the light arriving at the objective lenses at the front actually passes through – some is reflected. This happens with the light finally arriving at the viewer’s eyes at the other end of the binoculars as well – … Continue reading
Posted in BINOCULAR BASICS
Tagged coated, Coating of lenses, fully coated, fully multi-coated, phase-corrected
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Optical features of a binocular
All binoculars have the same set of optical features, whether small, normal size or big. These include lens coatings, close focus ability, field of view (FOV), focus speed, depth of view and ability to produce a bright image in dim light. These … Continue reading
Armoring of binoculars
Some manufacturers cover their instruments as far as possible in protective rubber or synthetic housing. These binoculars are known as “armored binoculars”. This protects the instrument from scratches and – very important – from bumps, which could harm the inner … Continue reading
Prism glass
Type of glass the prisms are made of: Bak-4 is a high density glass, of better optical quality than BK-7 and by far the best for making binocular prisms. Fortunately nowadays even cheap binoculars have Bak-4 prisms, whereas that would … Continue reading