for a circle of radius r is ‘1 rad’ the angle corresponding to length r on the circle,

say

accordingly :

:

for a circle of radius r is ‘1 rad’ the angle corresponding to length r on the circle,

say

accordingly :

:

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The diameter of the smallest disk that a lens can produce as image of a point size object is called Airy-disk

According to the so called “Rayleigh Criterion” holds:

The smallest possible Airy-Disk that a (diffraction limited) lens can generate is

The best possible resolution on image side (at 20% contrast) is the radius of this smallest possible Airy-Disk

When you double the F#, you lose factor 2 of resolution in each x and y direction.

If the lens supported 5 Megapixel before, then it supports only 1.3 Megapixel after

If the lens supported 5 Megapixel before, then it supports only 1.3 Megapixel after

When you double the wavelength (for example 850nm IR instead of 420nm blue), you lose factor 2 of resolution in each x and y direction. If the lens supported 5 Megapixel before, then it supports only 1.3 Megapixel after

See F-number

A normal lens has pincushion distortion or barrel distortion which can be corrected to give a perfect perspective projection, like the image of a pin-hole camera.

This process is called “rectification” and is often applied for stitchich images, for example, in panoramic photography.

The resulting images has no distortion.

** **

Ratio of the speed of light in vacuum divided by the speed of light in the current medium (eg, glass).

In other media the light is slower than in a vacuum.Say, the smallest refraction index is 1.
#

NOTE:

Glass refracts different wavelengths (“colors”) from different degrees.

Result is different refractive indices, “depending on the light color.”

As a result blue light takes a different path through a lens than for example red or green light!