After 15 seasons, the police procedural drama CSI is coming to an end, but not without having convinced viewers all over the world that they have the requisite chops to solve any crime by just looking for an errant hair while taking a few photographs.

But the video below goes someway to explain the real work involved in being a forensic photographer, giving an incredible behind-the-scenes look at the processes involved. And it’s all about seeing the light.

In order to capture the hidden details at a crime scene, these photographers utilise different light wavelengths to cast new light on what is otherwise hidden from view.

The video below shows Nick Marsh, a forensic photographer for more than two decades with the London MET Police Force, offering an insight into his work and just what it means to him. Check it out below: