PORTLAND — They called themselves Group f/64.

These innovative photographers from California — Ansel Adams, Edward Weston and Imogen Cunningham among them — challenged the soft-focus pictorialist style of their day, in the 1930s.

They maintained that modern photography should take on a new aesthetic — great field of depth, sharp focus, clean edges and bold forms. This “straight” or pure photography, as it came to known, starkly contrasts the then-popular romantic, hand-crafted pictorial style obvious in elegant portraits, tonalist landscapes and allegorical studies.

To accomplish this, they used the f/64 aperture (the opening in a camera through which light passes into the lens), hence the name of their group.

For these photographers, technique was more important than subject matter. And they applied the technique to many types of photographs: industrial, urban and natural landscapes, portraits of friends and fellow group members, and isolated objects for sharp-focus still lifes.

Examples of their once controversial style of photography — which is now accepted as an important photography movement of the 1930s — can be seen at the Portland Museum of Art through Dec. 5.

Outstanding works in the “Debating Modern Photography: The Triumph of Group f/64” exhibit are Weston’s “Shell;” Alma Lavenson’s “Self Portrait, Hands;” Irving Bennett Ellis’ “Sand Dunes;” and Margrethe Mather’s “Judith.”

These photographs feature sharp tonal contrasts, repeated surface patterns, skilled use of light and shade, and hard-edge lines. Poignant and starkly beautiful, they take your breath away.

Other works of great significance include a portrait of Weston taken by Adams outdoors in bright sunlight, accenting details of his face and the texture of his clothes; and a portrait of Jascha Heifetz by William Mortensen.

“Debating Modern Photography” is unique in that the showing of 90 works by 16 photographers includes examples of the pictorial style to better illustrate the debate. Kudos to the PMA for creating a section where negatives are displayed and another where wooden tripod cameras have been set up with different apertures, showing viewers the difference between f/64 (sharp and clear), f/11 and f/2(soft and blurred).

I highly recommend this exhibit for anyone interested in the history of photography and its development as an art form requiring creative insight, diverse viewpoints and excellent timing skills.

The museum at Seven Congress Square is open 10 a.m. to 5 p.m. Tuesday, Wednesday, Thursday, Saturday and Sunday; and 10 a.m. to 9 p.m. Friday. Admission is $10 for adults, $8 for seniors and students with ID, $4 for youths ages 6-17 and free for children under 6. Admission is free from 5 to 9 p.m. Friday.

Pat Davidson Reef has a master’s degree in education and has taught art history at Catherine McAuley High School in Portland. She has written two children’s books, “Dahlov Ipcar, Artist,” and “Bernard Langlais, Sculptor.”