SVS-Vistek exo174, Manual

Page: 29 / 160

SVS-VISTEK
Feature description 29
5.1.9 Resolution
As mentioned in the specifications, there is a difference between the
numerical sensor resolution and the camera resolution. Some pixels
towards the borders of the sensor will be used only internally to calibrate
sensor values (“dark pixels”). The amount of dark current in these areas is
used to adjust the
offset .
For calculating image sizes, the maximum camera resolution is
determining maximum image resolution. See
specifications of your
model.
5.1.10 Offset
For physical reasons the output of a sensor will never be zero, even the
camera is placed in total darkness or simply closed. Always there will be
noise or randomly appearing electrons that will be detected as a signal
(dark noise: noise generated without light exposure).
To avoid this dark noise to be interpreted as a valuable signal, an offset
will be set.
dark noise cut off by the offset
Most noise is proportional to temperature. To spare you regulating the
offset every time the temperature changes. A precedent offset is set by the
camera itself. It references certain pixels that never were exposed to light
as black. So the offset will be set dynamically and conditioned to external
influences.
The offset can be limited by a maximum bit value. If higher values are
needed, try to set a look up table.
In case of multi-tap CCD sensors, offset can be altered for each tap
separately (see tap balancing).