Advance look at two impressive documentaries

Insight and perspective are what good documentary-making is all about. I saw plenty of both - as well as some lack of both - at the Independent Documentary Conference I attended last week in Washington, cosponsored by the American Film Institute and the Corporation for Public Broadcasting.

The most impressive events of the conference were the showing of two documentaries the public probably won't be seeing for several months - ''Seeing Red: Portraits of American Communists,'' by Julia Reichert and James Klein, and one program about the Tet offensive from the 13-part PBS series ''Vietnam: A Television History.'' 'Seeing Red'

Though still to be tightened and polished, this is a sensitive investigation into the intellectual and emotional motivations of American Communists of the 1930s and '40s. It's a series of testaments by a wide range of early Communists who appear to be humanistically motivated and eager to be part of ''the heart of humanity.'' They were outraged by the suffering around them and joined what seemed to them to be the only protest group they knew much about. For them, joining the Communist Party in those days meant gaining status in their own conscience as well as a certain status within a secret intellectual peer group.

Those interviewed range from dock worker to secretary to writer. The film attempts to place all of this in the perspective of history - the 1930s depression, the fall of democratic Spain, the rise of Nazism and fascism.

The major fault in the film lies, perhaps, in the sameness of the people interviewed - all the Communists are ''good guys'' who claim to have joined the party for purely unselfish reasons. None have any major regrets, although most tend to believe they should have questioned more. Certainly there were other Communists who might have provided some variety - but it is probable that these were Communists who would rather not appear on camera, even before an obviously sympathetic filmmaker.

Another great lapse is the failure of the documentary-makers to take into account the enormous disillusioning effect the Russo-German pact of 1938-39 had on American Communists. The program instead attributes all the disillusionment to the later internal Soviet attack on Stalin.

There is still work to be done on the documentary, however, and perhaps before it reaches theaters and TV screens it will be perfected. But even as it stands it is an impressive adventure in perspective. ''Seeing Red'' is a peculiarly American tribute to individual human values in a democratic society. 'Vietnam: A Television History'

In many ways, ''Vietnam: A Television History'' is also such a tribute. It investigates the bureaucratic as well as the individual response to warmaking.

''Vietnam'' seems to be the ideal response by creditable newsmen to the contemporary trend toward questionable ''docudrama.'' It appears to substitute truth for wild conjecture and dramatic license. Its goal of providing enough factual material to allow viewers to arrive at knowledgeable interpretation is one that TV news viewers have every right to expect from the emerging electronic journalism. One hopes it is a harbinger of most future television news coverage.

Although I saw only the seventh in the 13-part WGBH Boston series - ''Tet 1968'' - I have read much about the series and talked to its executive producer, Richard Ellison, and its writer-correspondent, Stanley Karnow. Mr. Karnow, by the way, is the author of a companion book - which will be published simultaneously with the premiere of the series in the fall: ''Vietnam: A History'' (Viking Press, New York). Special viewers' guides will also be available to newspapers, as well as several teaching devices prepared especially for serious students of recent history.

''Vietnam'' is landmark television - an enormous amount of preparation went into it during its six-year gestation period. The staff and its many expert consultants engaged in extensive film and print research as well as in-depth interviewing of principals involved in the years - 1945-75 - covered by the series. Executive producer Ellison asserts that his program is ''the most accurate and complete television chronicle to date of the wars in Vietnam.

''The ''Tet'' segment is an impressively straightfor-ward account of the 1968 counteroffensive. It is filled with facts as well as background information. Included are some rather disconcerting sections about how President Lyndon Johnson decided not to run for the presidency again. All of this is strengthened with testimony by many of the actual participants in the events, ranging from generals to presidential advisers. Independent documentary-makers

I listened to much complaining at the documentary convention - mostly by independent filmmakers who want more grant money given them with no strings attached. They want freedom from interfering producers, editors, station managers, etc.

They also demand greater access to their audience - i.e., television air time. Everybody is disgruntled at the decrease in federal funding for CPB and PBS, which seems to have resulted in less money for the independents.

Although it is certainly true that commercial television is airing fewer and fewer documentaries, it is also true that TV viewers who go over the TV listings carefully will find an extraordinary variety of fine documentaries available on PBS. In many cases, however, it may be necessary for viewers to call local PBS station programmers and urge that certain documentaries be aired. (Documentaries previewed in this column are too often shown in only selected PBS-affiliated stations.)

So I encourage passionate partisans of the independent documentary who sometimes talk of boycott not to chop down PBS, the only shade tree in what sometimes appears to be an electronic desert.

Perhaps the ultimate answer lies in cable TV - in an independent-access channel on every new cable system, a channel that would give totally free access to any independent filmmaker who brought his film to the transmission studio.

That's what all of us - viewers and filmmakers alike - should be working toward. On and about the air

* Parents' Choice has just announced its annual TV awards: ''Fraggle Rock'' (HBO); ''Fame'' (NBC); ''Hill Street Blues'' (NBC); CBS News (for ''Sunday Morning'' and ''Bill Moyers' People Like Us''); ''Square Pegs'' (CBS).

* One of the best TV documentary series of the decade - ''A Walk Through the 20th Century With Bill Moyers'' - which was a victim of the recent CBS Cable debacle, has finally found its rightful place . . . on PBS. Through New York's WNET, the 20-part series which Moyers co-produced with the Corporation for Entertainment and Learning will be scheduled soon on PBS. Now, how about finding a slot in the schedule for the Entertainment Channel's superlative nature show, ''Animal Express''?

* Some fortunate cable-subscribing parents may find themselves in a system that is making the new Disney Channel available . . . for a fee of around $10 a month, of course. The 16-hour-a-day service, which starts up on Monday, will be delivered by satellite to scattered systems across the country.

While you can expect to see many of the old Disney favorites, don't expect to see them all - the problem of private videotaping of some of the most popular Disney movies will prevent the new channel from airing them until ''proper safeguards'' are worked out. Like jail for pirate tapers, maybe?