User manual

Small Vision System User Manual 17
2.1.9 Adjusting Video Parameters
Most framegrabbers support some kind of video image adjustments, such as contrast or brightness.
The video parameter dialog is invoked using the Video… menu item (Figure 2-4).
Most analog cameras have automatic adjustment of exposure and gain, which change according to
lighting conditions. The user can set brightness and contrast, which are framegrabber parameters that
change the processing of the analog signal.
The MEGA-D digital stereo head has manually controlled exposure and gain. Exposure is the time
that any given pixel is exposed to light before being read out. Gain is a amplification of the signal that
comes out of the pixel. In general, it is best to increase the exposure first, and if necessary, to increase gain
once exposure reaches a maximum. The reason for this is that gain will increase the video noise, while
exposure increases the pixel’s response to light. In some cases, though, short exposure times are desirable
for minimizing motion blur, and it may be more convenient to increase gain while exposure is not at a
maximum.
The values of exposure, gain, brightness, and contrast are all represented as a percent.
The colorized version of the MEGA-D digital camera can input color images, and the color balance
can be adjusted manually using the red/blue differential gain. More information about color processing is
in Section 2.1.12.
Figure 2-4 Video Parameter dialog box.