User`s manual

Operation and Features
BASLER A302
f 3-17
DRAFT
3.9 Shading Correction in the A302fs
In theory, when the camera captures an image of a uniform object, the values output from the
pixels in the camera should be uniform. In practice, however, variations in optics and lighting can
cause the camera output to be non-uniform even when the camera is viewing a uniform object.
The A302
fs monochrome camera is equipped with a shading correction feature that allows the
camera to correct the captured image for variations caused by optics and lighting. The camera
corrects for shading variations by applying a “shading correction table” to each captured image.
Shading correction is an advanced feature. Shading correction is enabled by setting the
ShadingMode field of the SHADING_CTRL advanced features register (see Section ).
3.9.1 Creating a Shading Correction Table and Enabling
Shading Correction
The A302fs camera does not directly support the creation of a shading correction table. A shading
correction table must be created by the user.
The Viewer Program included with the Basler BCAM 1394 driver provides tools that allow you to
easily create a shading correction table, to upload the shading correction table to the camera, and
to enable shading correction on the camera. The program also allows you to output the camera’s
currently stored shading correction table in the form of an image (direct reading of the shading
data in the camera is not possible). Instructions for using the Viewer Program to work with shading
correction are included in the BCAM 1394 Driver Getting Started Guide.
Before using shading correction, you should capture several images of a uniform gray target
under your normal lighting conditions and you should examine the pixel values in the captured
images:
• If the value of the darkest pixels is greater than 1/3 of the value of the lightest pixels, you
should enable shading correction with a 1:3 correction factor.
• If the value of the darkest pixels is between 1/3 and 1/5 (inclusive) of the lightest pixels, you
should enable shading correction with a 1:5 correction factor.
• If the value for the darkest pixels is less than 1/5 of the value for the lightest pixels, do not
use shading correction.
*
The camera can only store one shading correction table. When a new shading correc-
tion table is uploaded to the camera, it will overwrite the existing correction table.
If the camera is turned off and on again, the stored shading correction table is lost. A
new shading correction table must be uploaded into the camera.
Shading correction does not effect the frame rate.
A new shading correction table must be created and uploaded to the camera every
time a change to one of the following occurs: camera position, video format, video
mode, area of interest, gain setting.
Shading correction is an advanced feature and may not be supported by the camera
driver software that you are using to operate your camera.