Why a lower magnification power is large lens?

Magnification is the process of enlarging an object in visual size, normally through an optical lens.

To see the details of a tiny object or object, it is necessary to move the object closer to the eye, so that the angle of view can be enlarged to form a larger real image on the retina. But when the object is too close to the eye, it cannot be seen clearly.

Magnification is also an important parameter of the magnifier, but can not blindly believe that the higher the magnification isbetter, the choice should first consider the numerical aperture ofthe objective lens.

When the convex lens is used as a magnifying glass, the angular magnification is approximately equal to the apparent distance (about 25cm) and the focal length. For example, a magnifying glass has a focal length of 10cm, its angular magnification is 2.5 times times, and usually writes 2.5x

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What are the meanings of numbers and symbols on the magnifying glass? For example, 4X/16D/150/: where 4X/ represents the magnification, related to the refractive power of the lens. In general, the larger the multiple, the smaller the mirror surface of the lens, and the shorter the working distance when it is used. 16D/ represents the dioptric power, which is the performance of the light gathering power. For the reciprocal of the focal length, a +16D lens will focus the parallel light on the 1/16 meter. 150/ indicates the working distance, the unit is mm, refers to the distance between the eye and the magnifier, usually the greater the magnification, the shorter the working distance, the closer the eye will be to the magnifying glass.

When the magnification is large, the actual field of view is reduced accordingly. The larger the multiple, the smaller the area that can be observed at the same time. It is not conducive to discovering and finding goals, and it is particularly disadvantageous for observing observations that frequently change targets. Even if you have a good goal, the shelf will easily lose your goal if you shake it a little.

Magnification = Objective Focal Length / Eyepiece Focal Length