NINOX 640 II/USER MANUAL/09-20/REV1.1
8. CONTROLLING THE CAMERA (XCAP)
The sections below will give information on using each control of the Ninox 640 II, giving a
description on how to use each control parameter and their effect on the camera’s
performance. The software used to illustrate the camera controls is XCAP.
8.1 Exposure Time and Frame Rate
The exposure time and frame rate can be controlled under any camera control tab in the
XCAP GUI and remains constant on the GUI.
Exposure Time:
By default, the auto exposure control (ALC) will be enabled, meaning that
the exposure time and digital gain cannot be manually selected. The ALC will automatically
adjust these parameters based on the signal strength. The ALC can be fine tuned in multiple
ways. These controls are discussed in section 8.2.
If the ALC is disabled, the user will be able to set a fixed exposure time and digital gain,
using either the manual input box or the slider bar. The maximum exposure time that the
camera can perform is ~26.8s. However in practice, with the sensor only cooled to -15
ͦ
C,
the image would display a lot of dark noise at this exposure time. In practice, the maximum
useable exposure time is probably closer to ~5s. Regardless, the limit on the exposure bar
slider on XCAP is 26800ms. An exposure time can be set either using the user input box or
the slider.
The minimum and maximum exposure times that the camera can set are shown in the table
below in Figure 6.
High Gain
Low Gain
Min. Exposure Time
450µs
50µs
Max. Exposure Time
Frame Period – Readout Time
Frame Period – Readout Time
Maximum possible exposure time that the camera can perform is
~26.8s.
Frame Rate:
The frame rate can also be set using the frame rate user input box. By default,
the frame rate is set to 60fps. If an exposure time is selected that exceeds the exposure time
limit of the current frame rate set, then the exposure time will dominate, and the frame rate
will be decreased. Alternatively, if the user selects a frame rate that is too fast for the current
exposure time set, XCAP will decrease the exposure time.
Frame Rate and Maximum Exposure Time:
The maximum exposure time is a function of
the frame period (1/frame rate) and the readout time. The relationship between these three
parameters is shown below:
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝐸𝑥𝑝𝑜𝑠𝑢𝑟𝑒 𝑇𝑖𝑚𝑒 = 𝐹𝑟𝑎𝑚𝑒 𝑃𝑒𝑟𝑖𝑜𝑑 − 𝑅𝑒𝑎𝑑𝑜𝑢𝑡 𝑇𝑖𝑚𝑒
The readout time for the Ninox 640 II is dependent on whether the camera is in low (LG) or
high (HG) gain. The readout times for each gain mode are as follows:
Readout Time (LG) = ~6ms
Readout Time (HG) = ~10ms
Figure 6: Minimum and Maximum Exposure Times.
