The secret to a good thermal image
16
The comparison between photography and thermography can be summarized in a table
using a few keywords:
Photography
Thermography
Interesting motif
The object to be examined
“Tells a story”
“Presents facts”
Aesthetically pleasing
Clear heat patterns
Emotive
Objective
Image detail
Image detail
Focus
Focus
Lighting
Emission and reflection
Brightness
Brightness
Contrast
Contrast
As with photography, in thermography there are countless possibilities for editing images
—provided they are saved as radiometric images. However, not all settings can be
changed, and not all image errors can be corrected.
16.4
The three unchangeables—the basis for a good image
16.4.1
Focus
A professional thermal image is always focused and sharp, and the object and heat pat-
tern must be clear and easy to recognize.
Figure 16.1
Only hazy “patches of heat” can be seen in the unfocused image (left). The focused image
(right) clearly shows which object is being observed and where the object is warm.
A blurred image not only comes across as unprofessional and makes it harder to identify
the object and any faults (see Figure 16.1) but can also lead to measurement errors (see
Figure 16.2), which are more serious the smaller the measurement object. Even if all other
parameters are set correctly, the measurement values from an unfocused thermal image
are highly likely to be incorrect.
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