What was this group and why was it significant?
As others have already said, 'Group f/64' was made up of a number of photographers based in and around the San Francisco Bay area who formed an association in the 1930s to promote their similar style of photography that emphasized straight photography as opposed to the popular pictorialist style that had prevailed in photographic art circles for the first third of the 20th Century.
The defining moment for 'Group f/64' was an exhibit of a collection of photographs from its members that opened in 1932 at the M.H. deYoung Memorial Museum in San Francisco.
Posted with the exhibit of 80 photographs, 66 from the seven "members" of 'Group f/64' as well as 16 others from four like-minded "guests" of the group, was the following manifesto:
"The name of this Group is derived from a diaphragm number of the photographic lens. It signifies to a large extent the qualities of clearness and definition of the photographic image which is an important element in the work of members of this Group.
The chief object of the Group is to present in frequent shows what it considers the best contemporary photography of the West; in addition to the showing of the work of its members, it will include prints from other photographers who evidence tendencies in their work similar to that of the Group.
Group f/64 is not pretending to cover the entire spectrum of photography or to indicate through its selection of members any deprecating opinion of the photographers who are not included in its shows. There are great number of serious workers in photography whose style and technique does not relate to the metier of the Group.
Group f/64 limits its members and invitational names to those workers who are striving to define photography as an art form by simple and direct presentation through purely photographic methods. The Group will show no work at any time that does not conform to its standards of pure photography. Pure photography is defined as possessing no qualities of technique, composition or idea, derivative of any other art form. The production of the "Pictorialist," on the other hand, indicates a devotion to principles of art which are directly related to painting and the graphic arts.
The members of Group f/64 believe that photography, as an art form, must develop along lines defined by the actualities and limitations of the photographic medium, and must always remain independent of ideological conventions of art and aesthetics that are reminiscent of a period and culture antedating the growth of the medium itself.
The Group will appreciate information regarding any serious work in photography that has escaped its attention, and is favorable towards establishing itself as a Forum of Modern Photography."
Adams himself said, in a 1933 article he wrote for Camera Craft magazine:
Our motive is not to impose a school with rigid limitations, or to present our work with belligerent scorn of other view-points, but to indicate what we consider to be reasonable statements of straight photography. Our individual tendencies are encouraged; the Group Exhibits suggest distinctive individual view-points, technical and emotional, achieved without departure from the simplest aspects of straight photographic procedure.
The movement away from pictorialism to straight photography, as defined by 'Group f/64', dominated artistic photography in the United States from the early 1930s until well into the 1970s. It's influence had spread abroad by the 1950s and also was significant in other parts of the world.
Are there tenets of or lessons from this group that are important or useful for photography today even in the modern digital world?
Had Ansel Adams not been the primary "name" associated with 'Group f/64', I'm not sure we would hear anywhere near as much about them today as we do.
Many people like to invoke Adams as some kind of mystical compositional genius when they seem to have no clue whatsoever as to what his most significant contributions to the art of photography actually were. In reality, his ascendence to the throne of American photographers in the mid-20th century was all about his development of the zone system and darkroom techniques that allowed him, and those who learned from him, to successfully capture scenes that had previously not been printable on the papers available to photographers at the time.
That's not to say that Adams was a slouch when it came to composition. He certainly was not. But it doesn't seem to me that the way he composed was revolutionary at all. He more or less followed the general rules of composition that were prevalent at the time. Many of these 'rules' were learned by photographers from observing several hundred years worth of masterpiece paintings.
What was revolutionary about the work of Ansel Adams was the way he exposed and developed that allowed a scene with wider extremes between the darkest and brightest parts to be depicted in a photograph than could be done conventionally using the best films and papers available at that time. He also did it so that the things he wanted to emphasize were reinforced by the tonal values within the photograph.
It's not that Adams "saw" all these wonderful scenes in front of him that no one else had tried to capture before. Others had tried and failed to do much of what Adams did compositionally. Those failures were due to limitations of dynamic range and tonal control. Where Ansel Adams expanded the envelope was in the way he controlled the range of tonal values from pure black to pure white to fit the details in the scene into a tonal range that could be printed on existing photo papers while also drawing the viewer's eyes to the things he wanted them to see.
Adams' membership in 'Group f/64' probably contributed a lot more to the status of 'Group f/64' and most of its other members than membership in 'Group f/64' contributed to Adams' stature as a photographic genius for his innovations in exposure and darkroom techniques. To be sure, much of the work that the members of 'Group f/64' did would not have been possible without techniques created or enhanced by Adams. In many cases it was those techniques themselves that allowed 'Group f/64' members and their followers to do what they did compositionally.
Today many of us probably take the true contributions of Adams, his work regarding exposure and darkroom techniques, for granted. We don't remember a time before Adams' zone system when the images he created using those techniques were thought to be not possible to make. Yet many of us still refer to him as the greatest American photographer of the 20th Century without knowing exactly why we say he is.
As inkista quotes Cartier-Bresson in a comment to the question:
"The world is going to pieces and people like Adams and Weston are photographing rocks!” So influence/impact on their contemporaries, let alone ours, maybe not so much.
Where the influence of 'Group f/64' has the most impact for us today, perhaps, is in the technical requirements for things such as lenses and recording mediums, and in the proper use of them, that the 'Group f/64' style required (and that pictorialism which preceded it did not). Even as Cartier-Bresson and others like him began emphasizing humans in their sociological/historical contexts and often in motion - rather than static scenes in nature - they accepted some of the basic tenets of straight photography that had been popularized by 'Group f/64':
- Sharply focused
- Carefully framed
- Precisely exposed
Many of us still place a good deal of emphasis on those things today.