'REALITY" has invaded TV, and it's not all it's cracked up to be.When the medium began sporting the video-verite look a few years ago, some viewers thought that here, finally, was TV's grim reckoning with life - an antidote to sitcome fluff. But after a diet of "real-life" programming, viewers of this misnamed format have ended up less sure of what "truth" on TV is than when the fad started. There are a few honest exceptions, like "Cops" on Fox, but the problem is that the use of actual on-the-scene footage - and especially the faked versions of it that have become epidemic - may be called "reality" TV, but they do not equal realism because they don't offer the whole story. Those documentary clips are single trees in a forest too big and complex for most TV formats to accommodate. In the hands of many TV producers, "actuality" footage tends to become a production device - along with music, narrative, and editing - to be used toward an end that is often very far from an honest search for truth, or even for facts. On shows like "Hard Copy," "Inside Edition," and "A Current Affair," they result in a hyped-up, "True Detective"-style magazine format that purports to present tough-minded exposes but instead merely gives gossip a serious-minded look by flashing lots of news clips. ABC's "Prime Time Live" and "20/20" have done fairly well in ratings, but they're not "reality" shows in the same sense. Reality TV requires something faintly grimy, a feeling that the camera is poking into places it rarely ventures and perhaps shouldn't even be found. Ages before the TV era, the old radio show "Gangbusters" used to offer a little of this feeling. One time they aired a confession, recorded by the police, from a young man whom the show bombastically announced had "since been electrocuted." The recording was clearly the real thing, but it was offered as just a juicy item to keep people listening. At least "Gangbusters" was honest about it. On many "reality" shows today they try to make you feel you're penetrating beneath a veneer to see a more honest picture than "straight" news gives. Yet the truth is manipulated as freely as it is in any docudrama with unabashedly scripted dialogue. To use "reality" material with any credibility, you need a show like "911," lightweight as it often is, where actual crises are described, re-enacted, and then talked about by the people who lived them. 911 calls to police and fire-departments are aired for realism, but the show deliberately pulls away from the event a little, removing the onus of naturalism and providing some perspective. It lets the people involved use the reality of their experience - and that's the key, using it - to achieve something more: in this case, an insight into human coping. The best filmmakers sometimes use reality clips, but they're after something truer than facts - an insight gained when realism has the right context.