Many thermographers are unaware that they are able to manually control the temperature scale on their thermal imager. Others are simply unwilling to adjust it because it adds another layer of complexity to operating the camera. As a result many operators simply revert to the “auto adjust” algorithms which can potentially leave a high number of exceptions undetected. Any point and shoot thermographer can find the obvious exceptions, but it takes a skilled operator to find the not so obvious exceptions.

The scale function has a number of guises depending on the manufacturer. It is known as:
Level/span
Tmax/Tmin
Range/Window
Gain/Offset
Brightness/contrast

Whatever the nomenclature in simple terms this function controls a thermal imager’s sensitivity. If the range is too wide, the thermal sensitivity is poor and the image will be undersatured. If too narrow, sensitivity will be too great and the image oversaturated. Either way, the ability to detect subtle Delta T’s will be inhibited.
The problem with using a thermal imager solely in AUTO mode is that environmental factors and other targets can cause the span to be too wide or be at the wrong level, providing insufficient information over your target of interest. While images can be post processed on your PC to adjust the scaling, if it isn’t set correctly in the field you may miss identifying/discovery the exception completely.

AUTO SCALE ADJUSTMENT
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OPTIMISED SCALE
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AUTO SCALE
Sub Zero Sky temperatures cause camera to scale poorly in auto range.
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OPTIMISED SCALE
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AUTO MODE (note the range)
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OPTIMISED SCALE & PALETTE ADJUSTMENT
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