Chapter 5
Image Sensor
NI 177x Smart Camera User Manual
5-4
ni.com
Figure 5-2 shows what happens when gain is applied to a signal.
Figure 5-2.
Effect of Gain on the Video Signal
In Figure 5-2a, low gain has been applied to the signal. The pixel values in
the image are grouped close together. In Figure 5-2b, medium gain has
been applied to the signal; there are now more notable differences in pixel
value within the image. In Figure 5-2c, high gain has been applied to the
signal; at high gain, mid-range and bright portions of the image are now
both represented as white, the highest pixel value. In Figure 5-2c, several
bright areas of the image have been clipped to the maximum pixel value,
and you can no longer distinguish subtle shading in the brightest areas of
the image.
Gain can be useful when there is not enough available light and you need
to increase the brightness of your images. However, increasing gain
multiplies both the signal and noise. When possible, it is preferable to add
additional lighting.
Auto White Level (NI 177xC Smart Cameras)
NI 177xC Smart Cameras allow you to adjust the gain for each color plane
in the RGB color space. The white level specifies the point at which values
in the red, green, and blue color planes converge to produce white. To
obtain an accurate white level, either adjust each gain value manually or use
automatic white level adjustment with a test image. For best results the
image should contain a neutral reference, such as a gray piece of paper or
a reference card.
a
Low Gain
b
Medium Gain
c
High Gain
255
Pix
el V
a
l
u
e
255
Pix
el V
a
l
u
e
255
Pix
el V
a
l
u
e
a
.
b.
c.
