For hazardous applications such as establishing the health of electrical components at a substation, the ability to measure temperature accurately over a distance is critical. Achieving this depends on several factors and two of the most important are the resolution of the detector and the chosen camera lens.
You can compare resolution to human eyesight. If you have 20/20 vision, you can define the smallest letters at the greatest distance and that’s the equivalent using an infrared camera with a high-resolution detector. A low-resolution detector is the same as a person whose sight is low on the visual acuity scale. The vision is improved by glasses and in the case of the IR camera by adding a magnifying glass to optically reduce its distance from the target.