Photo finish

Although some sports use electronic equipment to track the racers during a race, a photo is considered the most important evidence in selecting the winner.

Every part of each racer's body is shown as it appeared the moment it crossed the line; anything stationary is represented as a horizontal streak.

The final image often shows a solid white background, which is a continuous scan of the painted finish line.

Single-exposure photo-finish images are made by a camera positioned at the finish line; this was initially applied to horse racing.

The camera's shutter, which captures 136 images each second, is triggered as a horse breaks a thin thread on the race track.

[2] Historically, motion picture cameras had been used in the United States since the 1920s for recording race-meets but were unsuitable for photo-finish photography as the frame rate was too low to catch the critical instant when horses or dogs reached the finish line.

The strip film moves across the slit in the same direction to the race and at substantially the same speed as the rate of movement of the image of the horses as each passes the finishing line.

This provides a precisely aligned image showing both sides of the horses, and a set of stripes left by the neon 100th/sec intervals for accurate timing.

A battery of electronic devices are installed in high-profile events (such as the Olympic Games) to ensure that accurate timings are given swiftly both to the spectators and to the officials.

[10] After a close sprint final in the Men's under-23 road race at the 2010 UCI Road World Championships in Melbourne, the organisers had to declare a dead heat between the two riders finishing just behind race winner Michael Matthews and runner-up John Degenkolb, as they were unable to detect any differences on the images taken from Tissot’s photo finish camera.

On February 17, 2018, Tyler Reddick beat Elliott Sadler by 0.0004 seconds to win the PowerShares QQQ 300 race in the NASCAR Xfinity Series.

A photo finish decided the winner of the 2005 running of the Japan Cup, which was given to Alkaseed, narrowly defeating Heart's Cry.

In 2011 with new digital technology recording vision at 10,000 frames per second, Dunaden was declared a winner over Red Cadeaux in the $6 million Melbourne Cup.

And in the 150th running of the Kentucky Derby in 2024, Mystik Dan edged past Sierra Leone and Forever Young in one of the closest three-way photo finishes at any horse racing event.