SVS-Vistek HR Series, Manual

Page: 48 / 102

SVS-VISTEK
Feature description 48
In theory there are several ways to correct shading:
>
In the host computer: Significant loss of dynamic range, colour
ruptures
>
In the camera, digital: better (smoother) shading than on the
computer side (10 or 12 bit), loss of dyn range
>
In the camera, analog: Change gain/offset locally on sensor to get
optimum shading correction with only small changes in dynamic
range
6.2.19 Shading Correction Tool
Images taken with shading correction will seem to have a perfectly
balanced illumination. The original idea was to correct the shading of
sensor and lens, but it can be used to correct shading of illumination (a
non-homogenous illumination) as well.
Shading correction is not a replacement for correct illumination. It is
important to have in mind that illumination shading correction might
reduce dynamic range of the images taken. By using different gains and
offsets on the sensor local noise might be less uniform. Structures in the
reference image might lead to visible shading artifacts.
In contrary to any shading correction being done after image recording,
the method described here will hardly affect the dynamic range of the
image.
The task is done with shading maps. Being applied before final pixel
quantization, a significant improvement in image quality is the result.
SVCamImgCorrTool (you might download this from the SVS-Vistek
download center ) will help you through this task.