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- Thermal imaging camera technology: resolution, NETD, focus & IFOV | Testo
Thermal imaging camera technology:
What image quality really means
A thermal imaging camera is good when it reliably represents the measurement task. The target must be sufficiently large and sharp at the usual distance (IFOV + focus), small temperature differences must be visible (NETD), and results must be documented reproducibly.
Which technical specifications are decisive for thermography?
The key specifications are detector resolution, field of view/FOV and IFOV depending on lens and distance, thermal sensitivity (NETD), and focusability. Software, reporting and standardization complete the field workflow.
Detector resolution & geometry: how many measurement points you really have
Detector resolution determines the number of temperature measurement points per image. More pixels help when targets are small or far away.
Always consider target size and distance; resolution alone is not enough.
SuperResolution can improve detail rendering, but it does not change the physical measurement geometry.
Thermal sensitivity (NETD): making small differences visible
NETD in mK describes the smallest temperature difference the camera can display as contrast. The lower the value, the finer the visible differences.
When NETD is the limiting factor
NETD is especially important for very small differences on large surfaces or early anomalies. It often determines whether a pattern emerges from noise.
Optics, field of view (FOV) and IFOV: why lenses determine use
Optics determine the image section and apparent object size, so they are key for measuring small targets at greater distances.
Wide-angle lenses suit large areas; telephoto lenses enlarge small targets from greater distances.
IFOV determines whether an object can be measured meaningfully; at 1–2 pixels a mixed pixel is created.
Focus, image stability and measurement accuracy
Blur spreads temperature information across pixels, making hotspots, boundaries and measurement points unreliable.
Manual focus is useful for changing distances and small targets; automatic focus must be checked with low contrast or reflective surfaces.
Blurred edges can make values vary, so focus belongs in the standard workflow.
Analysis, software & standards in the field
Technical image quality is only the beginning; image management, reproducible measurement points and standardized reports are decisive.
Standardized reports, clear measurement-point logic and image management improve recurring electrical, maintenance and PV inspections.
Apps support on-site documentation, data sharing and workflows; connectivity features speed up analysis.
Overview of Testo thermal imaging camera features
Next steps: technology requirements, software and instrument comparison
After defining the application, deepen the fundamentals (ε/RTC/IFOV), define a reproducible documentation workflow, and choose a camera whose resolution and lens match object size and distance.
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