Digitalgain - Smartek Vision Giganetix GC Series User Manual

7.2.2 Digital Gain
The pixel signal received from an image sensor is amplified and digitized before transmitted to the host
application. For devices which do not provide an individual analog gain separately for each color channel,
or in applications where the available maximum analog gain does not suffice, a software based gain can
be applied by the ImageProcAPI. The digital gain is a factor which is multiplied with each pixel value of an
image channel, generating the new value of the pixel:
Each channel has its own gain value, which makes it for example to a tool for white balancing, if not already
supported by the camera.
Further, digital gain is a useful feature to enhance the image brightness, especially under low light condition.
Increasing a digital gain value means increasing the intensity of each pixel, resulting in a brighter overall
image. However, the image noise will also be increase with digital gain.
Figure 138 demonstrates four different gain settings applied to the image. While digital gain equals 1.0
represents the image at its original, with increasing digital gain value, the image becomes brighter and the
noise rises as well. Also at higher gain settings, some pixels are over-saturated what leads to information
loss in the image.
Digital Gain = 1.0
In contrast to the analog gain the digital gain produces "holes" in the histogram, shown
Note
in Figure 139. As the multiplication takes place on the digitized image with the same
bit depth as the output image, some luminance levels cannot be reached anymore.
Pixel(x, y) = Pixel(x, y)
out
Digital Gain = 2.0
Figure 138: Digital Gain to brighten an image
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7 Image Processing in GigEVisionSDK
× DigitalGain
In
Digital Gain = 3.0
SMARTEK Vision Giganetix User Manual Version 2.1.4
Digital Gain = 4.0