IPI Infrared Cameras, Infrared Training and Infrared Products

For thermal imaging systems, one of the most critical specifications to be considered is resolution and spot measurement size. Spot size is a specification that pertains primarily to quantitative thermography. If you intend to present temperature measurement in your reporting and analysis, your camera’s resolution and resulting spot size is of ultimate importance.

Spot size will vary between different models of imagers and it cannot be changed. Although spot size is primarily a quantitative issue, it is important to understand its importance prior to purchasing an imager or prior to capturing data that may be quantitatively analyzed in the future.

When attempting to measure temperature, spot size determines a radiometer’s ability to accurately measure temperature. Spot measurement size is defined as the area from which temperature data are derived. This is a combination of an imagers detector resolution, detector pitch size, lens angle and proprietary measurement algorithms. Spot size is NOT determined by display crosshairs, laser dots, etc.

Detector Resolution is the principal determinant of spot size, as the greater the number of measurement points equates to a higher density of measurement points over a given area. Of course it is only part of the equation, as the lens angle and manufacturer’s image processing programming will determine the actual spot size over a given area.

Common resolutions include:

120×120 = 14,400 measurement points (very basic resolution)
160×120 = 19,200 measurement points (low resolution)
320×240 = 76,800 measurement points (professional resolution)
384×288 = 110,592 measurement points (high resolution)
640×480 = 307,200 measurement points (very high resolution)

Speak to a qualified professional about your target size, distance of measurement and determine the appropriate spot size for your target.