Abstract
The rise of apparent temperature in the thermograph as the detector is scanned across a temperature discontinuity is shown to be approximately exponential and to depend on the time constant of the circuit, the rate of scanning and the field size. The implication for clinical thermography is that the rise in temperature over a narrow region will be underestimated and such a region may not then be 'resolved' from the surrounding body surface. The effective response is estimated from measurements of the apparent temperature of the sources at the same black body temperature but of different width, and curves indicating the limits of resolution are derived. The relevance of the number of lines scanned in a frame and the definition of the image are also considered.