# Depth of Field

range in working distance for which the image is (acceptably) focused.

The largest depth of field (namely infinity) we get when we focus the lens to the so called hyperfocal distance. The focus extends from H/2 to infinity.

Take a quiz:

# Depth of Focus

Image side equivalent of the DOF (Depth Of Field), so it is the range of acceptable sharpness on image side, the range within which the Airy Disk stays within the COC (Circle Of Confusion).

# Diffraction Limit

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

# dispersion

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

Dependency of a measure on frequency / wavelength. (C) Wikipedia, zum Animieren bitte klicken

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

# Dispersion 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 