Written by Stella Ko, CNN Contributors Yoko Wakatsuki, CNN

Their almond-shaped eyes stare blankly into space. The ambivalent corners of their mouths leave their moods utterly indiscernible.

These wooden masks, used in an ancient form of Japanese theater called Noh, were made to be expressionless. But performers are charged with using slight and subtle movements to reveal the hidden emotions carved into each one.

Dating back almost 1,000 years, Noh is a style of musical drama with plots ranging from Japanese legends to modern-day events. Its masks, carved from blocks of cypress, are a key part of the tradition, representing figures like demons and monks. Actors are able to portray their characters' feelings by changing the angle and orientation of their heads.

'Humans try to hide their emotions'

Eighty-year-old Toshiro Morita has been photographing various forms of classical theater and theater masks since 1964. Coming from a family of photographers, he has published more than 20 books on Noh and the dance-drama tradition of Kabuki.

In his small suburban apartment he showed CNN hundreds of negatives taken over the past five decades. Most of his pictures were taken using a film camera, and aside from those published in books, haven't been digitized.

Using only natural light, Morita photographs Noh masks in front of a simple black background. Given their lack of expression, the slightest change in perspective and lighting can bring out a multitude of new emotions.

He prefers to hold his camera, instead of using a tripod, allowing him to easily adjust the angle -- and therefore the mood -- of his shots.

"Humans try to hide their emotions," Morita said. "But masks don't tell you anything (so) I can depict what I want."

A third-generation photographer, Morita grew up watching various types of theater, and was inspired by his father and grandfather's images of Japanese stage arts. After experimenting with surrealist oil paintings, he decided to continue the family tradition after graduating from art university.

Historically, mask making was not a profession in its own right. Performers would instead ask local carpenters to create custom masks featuring unique, neutral expressions.

Masks carved from blocks of cypress are a key part of the Noh tradition, representing figures like demons and monks. Credit: Toshiro Morita

According to Morita, it was important for mask makers to have a relationship with the wood they gave life to. But the craft has changed in recent years.

"That's why older masks have a lot of variation," Morita said. "But there is no originality in modern masks. They are just copying historic ones.

"A Noh mask is the face of an actor and can never be parted (from it). Actors puts them on inside the dressing room and the performance starts from there. Most people only see the performance on stage, but actors are already immersed in their roles from when they first face the mirror."

The importance of masks

With roots going back to the 12th century, Noh developed from ancient ceremonial dramas performed at shrines and temples.

But, like many traditional performing arts, Noh is struggling to attract interest in modern Japan. The Nohgaku Performer's Association, an organization representing Noh actors, told CNN that its membership has dropped almost 20% in the last 10 years.

In 2001, Noh was named a "Masterpiece of the Oral and Intangible Heritage of Humanity" by UNESCO, with some of the top practitioners now labeled "Intangible Cultural Assets" by the Japanese Government.

Among them is Noh actor and mask carver Michishige Udaka, who founded the International Noh Institute in 1986. As well as publicizing and preserving the theater's traditions, Michishige is committed to discovering a generation of new performers.

"I come from a family deeply rooted in the tradition of Noh," he said. "I felt honored to be part of that family, and I renewed my vow to maintain the tradition of my ancestors.

Having performed Noh since the age of 6, Michishige has a lifelong understanding of the subtle movements required to communicate with audiences. By tilting the mask up, for instance, actors appear to be smiling or laughing, while tilting downwards can express sadness or frowning. Performers may also use props likes fans, covering parts of their face to demonstrate shyness.

Photo shows Udaka Michishige in the play Nonomiya. The Magojiro mask he is wearing is carved by Michishige himself. Credit: Photo by Fabio Massimo Fioravanti

"Noh masks are not mere props but the face of living human beings," Michishige said.

A self proclaimed fan of Morita's pictures, Michishige describes the photographer's work as "very special."

"I think he sees between the real world and the world of emotions," Michishige said.

"He shows his understanding in his photographs. He can find those gray nuances. He shows a world that is invisible to the human eye through the lens of his camera."