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Tail Rejection: The Tail Rejection parameter defines the percentage of the total number of pixels
in the array that will be excluded prior to histogram equalization. The user-selected percentage of
pixels will be removed from both the bottom and top of the 14-bit histogram prior to AGC. This
feature is useful for excluding outliers and the most extreme portions of the scene that may be of
less interest. FLIR recommends tail rejection settings less than 1% to avoid the exclusion of
important scene content. Tail Rejection ranges from 0 to 10 percent and affects all dynamic AGC
modes by not using the upper and lower tail rejection percent in the AGC algorithm. This allows
for the removal of anomalous pixels from skewing the AGC away from actual information.
Enhancements:
Digital Detail Enhancement (DDE): DDE is an advanced nonlinear image processing algorithm
that preserves detail in high dynamic range imagery. The detail is enhanced so that it matches the
total dynamic range of the original image making the details more visible. Use Factory Defaults
to recover from inappropriate settings.
Active Contrast Enhancement (ACE): The Active Contrast Enhancement (ACE) feature
provides a contrast adjustment dependent on the relative scene temperature. ACE thresholds
greater than 0 impart more contrast to hotter scene content and decrease contrast for colder scene
content (e.g. sky or ocean). ACE threshold less than 0 do the opposite by decreasing contrast for
hotter scene content and leaving more of the gray-scale shades to represent the colder scene
content. ACE can range from -8 to 8 where -8 decreases contrast in darker regions while +8
increases contrast in darker regions.
Information Threshold: The information threshold parameter defines the difference between
neighboring pixels used to determine whether the local area contains "information" or not. Lower
thresholds result in the algorithm determining that more of the scene contains information,
resulting in more areas included in the Information-based algorithm and given a higher weighting
in the Information-based Equalization algorithm. Decreasing the threshold will result in imagery
approaching the appearance of the Plateau Equalization algorithm. Increasing the threshold will
result in a more information-dependent image, that is the flat portions of the scene (e.g. sky or
sea) are given less contrast and the pixels exceeding the information threshold will be given more
contrast.
AGC ROI: FLIR cameras allow the user to set a Region of Interest (ROI) or a rectangular area of pixels
on the sensor array that the AGC algorithm will use for its calculations. The AGC ROI applies to the
Automatic and Linear Histogram algorithms. The ROI can be set for either the entire frame size (-
320,256,320,-256) or some smaller portion. The ROI tab provides both a Window Editor and text entry
coordinates to control the size and location of the Region of Interest (ROI). The Set button must be clicked
for any changes to take effect. The AGC ROI is one of the most significant factors in improving image
quality. It can be used to ignore the sky or other large objects that would otherwise be used for calculation
of AGC.
The information contained in this document pertains to a dual use product controlled for export by the Export Administration
Regulations (EAR). Diversion contrary to US law is prohibited. US Department of Commerce authorization is not required prior to
export or transfer to foreign persons or parties unless otherwise prohibited.
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