Determining Factors in Image Quality

Obviously, the quality of the image you will be seeing through your optical device will be an important consideration in choosing your binoculars or scope. The following factors are the contributing factors to that image quality:

 

o       Magnification: The degree of enlargement of the object being viewed is an obvious consideration in choosing your instrument, and is known as the magnification. When using a spotting scope, the magnification power of 20 to 35 times the object size should be adequate for viewing during normal daylight conditions. Of course, scopes can deliver higher magnifications (up to 250x), but the more you magnify the image, the fuzzier it will become. Binoculars will typically magnify your image 7 to 10 times the object’s size.

 

o       Diameter of the Objective Lens, or Aperture: The size of the diameter of the objective lens determines how much light it gathers. More light produces a brighter, and therefore clearer and more detailed, image.

 

o       Focal Length: The distance between the main lens or mirror and the point where the light rays from the image come into view is the focal length. The longer the focal length in the scope or binoculars, the larger the image will appear.

 

o       Field of View: The field of view is the size of the area that is seen while looking through the scope or binoculars. Typically measured in linear feet, the field of view refers to the width of the area that can be observed at 1000 yards. The larger the field of view, the larger area seen through the scope or binoculars. The field of view is determined by the eyepiece design of the instrument.