Arthur C Clarke’s ‘third law’ states that any sufficiently advanced technology is indistinguishable from magic. Computer vision is the processing of images or video by computer to extract useful information. A technique termed ‘Eulerian magnification’ involves amplification of tiny movements from video recordings, so that very small motions can become visible to the human eye. This has the potential to detect tremor that is of such small amplitude it cannot otherwise be seen. Crucially, the only hardware required is a camera and computer processor, items that are ubiquitous. There is only one previous report of Eulerian magnification applied to a simple video of a Parkinson’s patient, but Parkinsonian signs could clearly be seen in the pre-processing video, and no control video was shown. We present remarkable video in which no tremor is seen in either patient or control before processing, and yet a Parkinsonian tremor is revealed in patient but not control after amplification. Blinded clinician ratings detect a greater number of Parkinsonian tremors after computer processing. Furthermore, we report a method using an ‘optical flow’ computing technique that records pixel motion vectors, and enables the computer to measure the direction and relative amplitude of this amplified movement.