Sample Photo Finish Image Note the time stamp "EPSOM R2 22 4 47" Image source Illustrated London News 1947
Throughout my life I have heard the term Photo Finish but till recently I hadn't realised that there was an Epsom connection.
A dictionary definition of the term is:
A race in which the leading contestants cross the finish line so close together that the winner must be determined by a photograph taken at the moment of crossing.
While this sounds very simple the reality is that to get a clear and sharp picture of a fast moving object is technically difficult, especially using old-school film technology. The first use in a UK horse race was not until the 22nd April 1947 during the Epsom flat racing season.
The photographs were taken using a special camera with no shutter - instead a long strip of film moved past a narrow slit at a speed relative to the speed of the horses. The camera, which was housed in a room above the Judges' box, needed two operators - one to watch the race and judge the speed of the horses, the other to set the speed of the film using controls on the back of the camera.
Photo Finish Camera Image source Illustrated London News 1947
Opposite the camera, on the other side of the track, was a Winning Post Assembly which contained (from bottom to top)
A drum, rotating at the same speed as the horses, showing the name of the racecourse, the number of the race and date, so date-stamping the image (in the top image EPSOM R2 22 4 47)
A flashing vertical light tube that produced a line on the photograph representing the winning line.
A tall thin mirror which would show the Judges the view from the other direction. (This mirror was not deployed at Epsom on the first day.)
As soon as the race was finished the film was quickly developed and a print produced for the race Judges.
The camera and system were first developed by The Race Finish Recording Company (now called Racecourse Technical Services Limited or RaceTech) which has continued to develop the system, so with up-to-date digital equipment the Judges have results within a few seconds.