Gwen Isaac during filming with her 2-month-old daughter, Hope. "She cost me a lot of money in sound mixing with her gurgling."

A candid film about a family's experience with terminal illness is to debut at the New Zealand International Film Festival this week.

Gwen Isaac spent four years filming Where There is Life, which follows Margaret Lee, from Eastbourne, and her family after she was diagnosed with motor neuron disease.

The Lower Hutt documentary maker described the film as a "warts and all" examination of the Lee family's collective experience of the disease as Margaret becomes more dependent on her husband, Stephen, for care.

"It's not easy watching, but it rewards the viewer. It allows them into a world [many] won't know anything about.

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"It's a tribute to he art of caregiving and a tribute to the human condition under pressure."

Filming began in 2011 and follows the Lee family as the disease takes hold of Margaret, who eventually died in 2014.

Isaac described the film as a "labour or love" and was feeling "excited and nervous" about the self-funded documentary's debut. Editing only wrapped in June.

She was let into the Lee's home after she met Margaret at the gym during her "going away do" after her diagnosis.

Filming the family once a week for four years, she became very good friends with the Lees.

She wanted to record the love and devotion shown by Stephen to his wife, and make a record of the family's final years together.

"I just really wanted it to be a film for Margaret. Margaret and Stephen and Imogen (the couple's daughter) allowed me to have intimate access to a very challenging time. They were all really supportive."

This is Isaac's first film despite having 13 years experience working in television in the United Kingdom and United States.

Much of the filming was done with Isaac's baby daughter, Hope, at her side which posed a few unusual challenges. "She cost me a lot of money in sound mixing with her gurgling."

Isaac said the the film gave viewers plenty to think about, broaching the topics of terminal illness, love and caregiving, and she would leave it up to them to determine what they took away from the documentary.

Isaac will tour New Zealand with the film after the NZIFF, with the aim of getting it accepted into more festivals.

*Tickets to the third screening of the film in Petone screening have sold out but seats to two screenings at Wellington's Nga Taonga Sound and Vision are still available.