Shading

Shading describes the loss of intensity from the center of an image to the corner.

According to the basic photometric law, all lenses lead to a loss of intensity from the center of an image to the corner. Sometimes this loss of intensity is amplified by vignetting of glas mountings and other characteristics of the lens geometry. Especially by using wide-angle-lenses at maximum aperture, a loss of intensity from the center of an image to the corner is quite visible. Some cameras compensate for that by internal image processing, but that amplifies the noise in the corners. Therefore noise measurement i sadded into this module as well. A uniform illuminated target, e.g. a diffusor plate in front of an integration sphere, is captured. Cameras with extremly short focal distances show an irregular color reproduction over the image, that can be evaluated in camera RGB or Lab color space. The results can be displayed in a pseudo 3 dimensional way or in 2 dimensions combined with a colored indicator for the amount of shading. The OECF of the camera is used to calculate the shading in f-stops of the original scene instead of just reporting the digital value difference.

» video demonstration (german version, english version comming soon)