These cows, seen in daylight under an overcast sky on a cool autumn day, are grazing in a field of fairly short grass. Most of the herd are in milk and nursing calves: the closest cow has a substantial warm area over the udder, as well as her muzzle and eyes.

The right eye does not look as warm as the left. This is an artefact because of geometry: as a surface becomes almost perpendicular with the image plane, so its IR image becomes less faithful to surface temperature. This was a significant issue with early IR cameras, which showed objects like fingers with quite thick halos at their edges. Thankfully it is less apparent with modern systems.

Although not seen on this image, IR cameras are surprisingly good at detecting cowpats. This is because a cowpat remains relatively warm for some days, as its content decays. However I would not recommend IR as a means of finding a ‘safe’ path through many cowpats: as the skin thickens on them, their surfaces cool and would easily be missed by the camera but found by the foot.

The false horizon of the field has been detected well as an edge and shown by MSX processing, just above the cows. The warm patch above that, on the mid-left, is a farmhouse in the distance. Behind that the land slopes steeply upwards to a chalk Down, and the patchy trees on that are seen silhouetted against the cold sky.

Image captured using a FLIR One™ IR camera and iPhone 6. Standard ‘Iron’ palette, without further image processing.