Powers & Magnification - Best Binoculars & Spotting Scopes for Birding - Recommendations
Your bird watching and wild bird identification efforts will be realized by understanding basic terminology specific to binoculars and spotting scopes. Grasp the importance of binocular powers and magnification, lens diameter, field of view and more. You can then choose the best binoculars or best spotting scopes to fit your needs. The following information will be helpful as you decide which binoculars and spotting scopes are best for your birding and wild bird identification interests.
Binoculars and Spotting Scopes Terminology
Binoculars Terminology
Power/Magnification and Objective Lens Diameter (example 8x42)
The first number, the Power or Magnification measurement, is the degree that the object being viewed is enlarged. In this example, binoculars with an 8 power magnification will magnify the object 8 times larger than would normally be seen with your eyes. The second number, the Objective Lens Diameter, is measured in millimeters (mm). The objective lenses are the front lenses of the binoculars. The diameter of the lens determines the light gathering ability. A larger lens produces greater light gathering ability and therefore improved detail and image clarity. The power level affects the brightness of an image. A lower power will produce a brighter image.
Field of View
The size of the area visible while looking through a pair of binoculars is referred to as the Field of View. Generally a greater magnification or power will produce a smaller field of view. The angular field of view, expressed in degrees, is indicated on the outside of the binoculars. The linear field of view refers to the area that can be viewed at 1,000 yards, and is expressed in feet. A larger field of view translates to a larger area seen through the binoculars. Depending on your bird watching needs, a significantly larger linear field of view may not be important. Please remember, in most cases, the larger the field of view, the poorer the image clarity becomes, especially around the edges. Bear this in mind when making your choice. Bigger does not always mean better.
Close Focus
Close focus refers to the distance between you and the nearest object on which you can focus while still maintaining a good image and sharp focus. This term is normally applied only to center focus models which may need to focus both near and farther distances. Close Focus distance is a critical issue with bird watchers and observers of close subjects that tend to move around at varying distances quickly.
Exit Pupil
The diameter that of the beam of light, measured in millimeters (mm), leaves the eyepiece of a pair of binoculars is the Exit Pupil. The larger the exit pupil, the brighter the image obtained will be. Having a large exit pupil is advantageous under low light conditions and at night such as astronomical, marine or low light conditions.
Relative Brightness
Gathering and transmitting enough of the available light to provide a sufficiently bright and sharp image define the brightness of a pair of binoculars. Brightness is certainly one factor to consider when determining the best pair of binoculars for you, but is not usually the most important. After all, most of your bird watching likely will be during well lit conditions when birds are active.
Eye Relief
Eye Relief is the distance, measured in millimeters (mm), that binoculars can be held from the eye and the full field of view can still be observed comfortably. Those who wear eyeglass in particular benefit from longer eye relief. Normally a minimum rating of 15mm will be needed for those wearing eyeglasses.
Spotting Scopes Terminology
Spotting scopes are used when more magnification is needed or wanted than binoculars provide. Spotting scopes are used widely for birding, viewing wildlife and landscapes and other objects at a great distance. Much of the terminology and technical specifications specific to spotting scopes are similar to binoculars. For example, a 20-60x82 spotting scope has a zoom magnification range of 20-60x (20 to 60 times larger than the size of an image as would be seen by the naked eye) with a front lens diameter of 82mm.
The significant increased magnification of spotting scopes can take you well beyond the capabilities of conventional binoculars. That said, two factors, the atmosphere and the optical system of the spotting scope, should be kept in mind. Heavy air, dust, humidity, glare and wind and air currents during the day can all reduce image quality and the greater the magnification, the more drastic the reduction in image quality will be. Few locations allow you to use more than 60-80x during the day, so most spotting scopes stop at 60x. The optical system of a spotting scope will impact magnification also. As magnification is increased, some decrease in image quality will result, no matter the model. In this key area, as the old saying goes...you get what you pay for. So yes, if you want a spotting scope that is as clear and sharp at 60x magnification as it is at 20x, then expect to pay more. Keep in mind though that most spotting scopes are used at lower magnifications, usually around 30x-40x. This is more than enough for most applications and all but the least expensive and cheapest model will produce reasonable images in this magnification range.
Objective Diameter
Assuming that you are comparing two models of similar quality, the larger the objective lens, the more detail you can see and the better image quality your scope will deliver, especially at higher magnifications. However, a large lens of mediocre quality, no matter how large, will never equal the performance of a smaller, quality lens. If you aren't sure, opt for quality, not size.
Close Focus
Although not an absolute necessity, a spotting scope with a close focus of 20 ft or less can be useful, especially if you plan to use a spotting scope with a camera.
Eye Relief
As with binoculars, this is the distance your eye can be from the eyepiece and still see the entire field of view. As a general rule, you will need at least 14mm of eye relief to see the entire field of view with eyeglasses and people with thick glass lenses in their eyeglasses will probably need more.
Waterproofing
While not a necessity, a waterproof scope is terrific to have. The seals in a waterproof model also prevent the infiltration of dust and dirt and therefore add to the lifespan of the spotting scope.
Tripods
Due to its high magnification, handholding a spotting scope and expecting to maintain a clear, non-blurry image is virtually impossible. A spotting scope requires that it be supported to keep it steady. You may be able to sneak by at lower magnifications with a monopod or shoulder stock, but above 40x, you must use a tripod. And the larger and heavier the scope, the larger and heavier the tripod should be. As all spotting scopes are threaded in the same fashion as a camera and therefore should fit on any standard camera or video tripod, unless you prefer, you will not need to purchase a special tripod for your spotting scope.
Best Binoculars for Birding Recommendations
While the ultimate choice is one of personal preference, generally full size binoculars ranging anywhere from 7x30 to 8.5x50 are preferred and considered the most popular range in magnification and objective lens size for bird watching. For instance, binoculars with an 8x42 configuration feature a 42mm objective lens size which provides ample light gathering capabilities in even lower light conditions and an 8x magnification allows you to steady the binoculars much more readily than with significantly higher powers, making the task of bird identification easier. Some birders with steady hands may prefer 10 power binoculars or greater.
Please remember that as you increase the power of your binoculars, less light will be gathered and therefore the viewing field will be reduced as well. It is also very difficult to keep an image steady at very high magnifications using standard hand held binoculars. A tripod is often necessary to steady an image at higher magnifications. A good alternative though for those seeking the option of high power magnification is a pair of binoculars with a zoom feature. This gives you the option of higher magnifications without the limitations of fixed, high power binoculars that can be a bit unwieldy.
Best Spotting Scopes for Birding Recommendations
Most agree that the best magnification range for birding with a spotting scope is 20-40x. Much higher than 40x and the field of view is too narrow to be practical, with the added drawback of a dimmer image. Keep in mind that problems such as heat waves will increase at higher magnifications. If you do a lot of dawn or twilight bird observation, or if your area is often overcast and dim, a wider objective lens will give you a better image. So you will want to choose a lens of 77-82mm. However, a larger objective lens also translates to increased size and weight. Birders who are out mostly during the day and don't relish the thought of carrying a heavier instrument will want to consider an objective lens size of 60-65mm.
