User's Manual

The secret to a good thermal image33
Figure 33.8 A thermal image in automatic mode (left) and in manual model (right). The adjusted tempera-
ture interval increases the contrast in the image and makes the faults clear.
33.5.2 Palettes and isotherms
Palettes represent intervals with the same apparent temperatures using different sets of
colors. In other words, they translate specific radiation intensities into colors that are spe-
cific to a particular palette. Frequently used palettes include the gray, iron, and rainbow
palettes (see Figure 33.9). Gray tones are particularly suited to resolving small geometric
details but are less suited to displaying small differences in temperature. The iron palette
is very intuitive and also easy to understand for those without much experience in ther-
mography. It offers a good balance between geometric and thermal resolution. The rain-
bow palette is more colorful and alternates between light and dark colors. This results in
greater contrast, but this can lead to a noisy image for objects with different surfaces or
many temperatures.
Figure 33.9 Gray, iron, and rainbow palettes (left to right).
The isotherm is a measuring function that displays a given interval of the same apparent
temperature or radiation intensity in a color that is different from the palette. It allows you
to emphasize temperature patterns in the image (see Figure 33.10).
Figure 33.10 Foundation wall: connection between the old (left in image) and the new (right in image)
parts of the building. The isotherm highlights an area of air leakage.
33.5.3 Object parameters
As we have seen, the appearance of thermal images is dependent on the thermogra-
pher’s technique and choice of settings, and the look of saved radiometric images can
be altered by editing. However, it is also possible to change the settings that are relevant
for the calculation of temperatures. In practice, this means that the emissivity and re-
flected apparent temperature can be altered retrospectively. If you notice that these pa-
rameters have been set incorrectly or want to add more measurement spots, the
temperature measurement values will be calculated or recalculated according to the
changes (see Figure 33.11).
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