The Diffraction limit describes the maximum possible MTF / resolution that a “perfect” lens could possibly have

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The Diffraction limit describes the maximum possible MTF / resolution that a “perfect” lens could possibly have

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(from latin *dispergere*, “to scatter”, to disperse” ) :

Dependency of a measure on frequency / wavelength.

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Using a Prism dispersion leads to splitting of white light beam into individual colors. A rainbow where light takes different paths inside the water dropplets, depending on their wavelength is another “real world” example of dispersion.

Every optical medium / glass type has different refraction indices for the various wavelength of light. The number that describes how different the light paths of the various wavelengths are, is the Abbe-number.

UNder dispersion formulas you find the most common formulas

Each optical material (glasses, plastics, gases) have a different refraction index for each wavelength.

Instead of keeping long tables, it’s possible to describe the behaviour of optical materials by formulas.

here are the main formulas used :

**1: Sellmeier (preferred)**

**2: Sellmeier-2**

**3: Polynomial**

**4: RefractiveIndex.info **

**5: Cauchy **

**6: Gases**

**7: Herzberger**

**8: Retro**

**9: Exotic**

see

Optical Distortion

TV Distortion

Optical Distortion vs. TV Distortion

Barrel Distortion

Pincushion Distortion