In a hotspot imaging scenario, which image is more accurate, which shows the hottest temperature, and which shows the correct temperature?

• A. More accurate: Focus; Hottest temperature: Focus; Correct temperature: Neither
• B. More accurate: Out of focus; Hottest temperature: Focus; Correct temperature: Neither
• C. More accurate: Focus; Hottest temperature: Out of focus; Correct temperature: Focus
• D. More accurate: Out of focus; Hottest temperature: Out of focus; Correct temperature: Neither

Answer: (A)

Focusing affects how sharply the hotspot’s energy is captured and how accurately its temperature is represented. When an infrared image is in focus, the hotspot’s radiance is concentrated into a small area, so the peak value tends to be higher and the spatial location more precise. If the image is out of focus, the hotspot blur spreads that energy across neighboring pixels, lowering the maximum pixel value and making the hotspot appear cooler and less defined. That’s why the image that is in focus is the one that better represents the hottest temperature and provides the most accurate depiction of where that hotspot is.

However, determining the exact temperature of the hotspot requires proper calibration and knowledge of factors like emissivity, reflected temperature, distance, and atmospheric effects. Without those corrections, neither image can guarantee the true, correct temperature. So the best choice is that the focused image is more accurate and shows the hottest temperature, while neither image alone guarantees the correct temperature.