Audiences of dance and theatre productions often watch the final iteration of a show. Rarely are they privy to what goes on behind the scenes and the work put in by unseen members of the crew.

An upcoming exhibition by photographer Tan Ngiap Heng, titled Anatomy Of Performance, hopes to shine a light on this usually hidden world.

Tan, 50, spent 20,000 to 30,000 hours over four years documenting the rehearsal process of 24 productions by home-grown theatre and dance groups. These include Wild Rice, Drama Box and Singapore Dance Theatre.

The free exhibition, which comprises 24 black-and-white photographs and write-ups of Tan's observations over the years, opens on Thursday and runs till Sept 4 at Gallery I at The Arts House.

The project started after Tan's father suffered a stroke in 2010.

Having to juggle the demands of taking care of his aged parents, he could not take up his usual commercial photography jobs and was looking for something to do that had more flexible hours.

"It was catharsis for me. Being surrounded by creative people doing creative work was an uplifting experience," he says.

Interwoven with the photos are Tan's observations of the scene, such as shining a little spotlight on hairstylist Ashley Lim and other unsung heroes who are often not part of the performance on stage; and the different types of spaces used in productions, which range from conventional proscenium stages to unusual venues such as the Bukit Timah Rail Corridor.

These observations are the result of Tan being behind the scenes himself, taking publicity and production shots of various theatre and dance groups since 2000.

He spent his early years photographing performing arts groups for the Esplanade's now-defunct Arts Magazine and was the resident photographer of Singapore Dance Theatre in 2007 and 2008.

The treasure trove of images that he has captured over the years - alongside videos, interviews and scans of documents - are available as part of Work In Process, a digital archive managed by the Lasalle College of the Arts.

As part of the exhibition's programme, a panel discussion on Saturday, titled Putting Together A Performance, will provide a larger view of the performing arts. It will explore what goes into a dance and theatre production.

Besides Tan, panel members include Alvin Tan, founder and artistic director of The Necessary Stage; Kenny Wong, technical director of this year's National Day Parade; and performer and drama educator Patricia Toh. The panel will be moderated by theatre practitioner Edith Podesta.

Tan Ngiap Heng will also lead a one-hour guided tour of the exhibition on Aug 21.

He hopes the exhibition will shed light on the hard work involved in the performing arts. "I think people need to realise how rigorous creating art is. It is as serious as any business. It takes training, planning, management, time and rehearsal, and innovative people."

The exhibition is also meant as a tribute to the artists he met. Laughing, he adds: "I am basically a fanboy of the people in these images."