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De Di Do

Depth of Field

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

Image: Depth Of Field

Depth Of Field

DOF =  Far PointNear Point

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.

see also Bokeh

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

Dependency of a measure on frequency / wavelength.

Light_dispersion_conceptual(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.