These images are taken with a camera that has its Infra red blocking filter removed and so it is susceptible to light beyond the visible spectrum . Subjects that emit Infra red radiation are generally green and their output increases dramatically when energised by the sun. Hence this form of photography works well in bright summer sunshine when most self respecting photographers working in black and white would have put their cameras away.
Conversely night time cameras emit Infra red light and so can illuminate their subjects when normal daylight is not available
Digital infra red is very different to the old film days , the pictures are sharp and dramatic