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This file has been superseded by Field of View v Magnification chart (cropped).png. It is recommended to use the other file. It is recommended to use the other file. Please note that deleting superseded images requires consent .
The pupil magnification of an optical system is the ratio of the diameter of the exit pupil to the diameter of the entrance pupil. The pupil magnification is used in calculations of the effective f-number , which affects a number of important elements related to optics, such as exposure , diffraction , and depth of field .
In microscopy, the field of view in high power (usually a 400-fold magnification when referenced in scientific papers) is called a high-power field, and is used as a reference point for various classification schemes. For an objective with magnification , the FOV is related to the Field Number (FN) by
An example of the Landolt C eye chart (also known as the Japanese eye chart). Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision, while the ETDRS chart is designed for use at 4 meters. [16]
[3] [5] The magnification here is typically negative, and the pupil magnification is most often assumed to be 1 — as Allen R. Greenleaf explains, "Illuminance varies inversely as the square of the distance between the exit pupil of the lens and the position of the plate or film. Because the position of the exit pupil usually is unknown to the ...
Optical magnification is the ratio between the apparent size of an object (or its size in an image) and its true size, and thus it is a dimensionless number. Optical magnification is sometimes referred to as "power" (for example "10× power"), although this can lead to confusion with optical power.
A typical magnification for use in dentistry is 2.5×, but dental loupes can be anywhere in the range from 2× to 8×. [15] Optimal magnification is a function of the type of work the doctor does - namely, how much detail he or she needs to see, taking into consideration that when magnification increases, the field of view decreases.
Ranges of 1- to 16-times magnification are common. The greater the magnification the smaller the proportion of the original screen content that can be viewed, so users will tend to use the lowest magnification they can manage. [citation needed] Screen magnifiers commonly provide several other features for people with particular sight difficulties: