Archiv November 2009

Defraction limit using a digital camera

Tuesday, 24.11.2009

The resolution of a lens is limited due to diffraction in dependence of the aperature.

Die Auflösung eines Objektivs ist beubungsbegrenzt von der Blende abhängig.

In the picture you can see small sections (about 100 pixels wide) of a photograph that was taken with a 50mm lens from a distance of 5m from a laptop screen. We see significant uncertainty in the larger aperture numbers (22). The lower quality in Aperture 1.8 is due to other aberrations.

Due to the diffraction limit the diameter of a pixel is d = 2.44 · ? · B, where F-number B and the wavelength ? determined. With a typical value of ? = 555nm we obtain d = B · 1.3?m. The typical pixel size of today's digital SLR cameras is about 5?m, so that we reached at f / 4, the theoretical limit. Digital Cameras have in some cases significantly smaller pixel sizes because they work with smaller image sensors.

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