French philosopher-critic extraordinaire, Roland Barthes, once said, "A photograph is always invisible, it is not it that we see." Not the photograph, but the vista; the place, the moment. How French. But how true.

Some of the more interesting photo-sharing groups on Flickr have recently been challenging users to give new life to original photographic documents from bygone eras. Depending on the precise form, these re-imaginings can take varying shapes, but they all tend to play on the aesthetic qualities of vintage imagery as well as the content therein portrayed. Take the 'Looking into the Past' group, which was featured on the Flickr blog last week (and on Wired last year).

The photographs contributed to this group show the photographer's hand holding an old (usually black-and-white) snap in the foreground with the contemporary, high-definition colour version forming the backdrop. It's like slapping a visual slice of history into today's world, and the concept has quickly captured people's imaginations. In unknowing homage to Barthes, these photographers are re-emphasising the locality of each image, and showing its life in time as well as space. The most enthralling contributions show something or someone which is now long absent, meaning that shoving the old photograph in the way of today's reality isn't just a neat trick, but an attempt at imaginatively re-igniting the original moment that inspired the picture - and maybe even re-connecting with the previous photographer who stood on the same spot all those years ago. It's all got very séancey, hasn't it? Anyway, this Polish photographer does a similar thing but realised with an intuitive roll-over effect on his blog. No need for holding hands round a table in the dark there, then.

Flickr has been considered a temple of retrospective photographic appreciation for some time now. The above technique was inspired by a rather more satirical venture - Michael Hughes' 'Souvenirs' project. There is an overt attempt to highlight the act of taking each photograph in these examples, but quite different is the impulse to upload old photographs and simply let them speak for themselves. Often this is concentrated on particular photographers or historical events (as in this example), but some of the most interesting groups are more purely whimsical and effortless than that. Among the thousands of images uploaded to the 80s! group, many are just plain old family snaps, advertisements and bits of packaging from the electro-plastic decade - these alone adequately represent our bohemian love affair with retro aesthetics. Quite a few of the photographs in this set are admittedly uninspiring and vague gestures at stereotypical notions of what the 1980s looked like, but many are much more intelligent than that. These ones stand out as truly admirable efforts to document the feel of something which is otherwise irrevocably lost to us.

Slightly different in purpose, but equally intriguing, is the 'indie retro & vintage-ish chic' group whose 721 members (at the last count) inspire each other with portraits and portrayals made to 'look old' through Photoshopping and the imposition of special tonal palettes, blurred edges and warmly fuzzy bursts of lens-flare. Some seem gimmicky, some are truly beautiful. But this sort of thing is terribly subjective so you'll have discover which is which on your own.

So 'remixing' vintage photography is starting to blossom as a popular trend. Maybe it was partly the throwback tendencies of our age that encouraged the curmudgeonly David Bailey back to photography after decades of abstinence (which began with his famous attempt to burn his life's work in 1979). Frustrated at where his creativity was going, and at the commercial demands his profession made of him, isn't it telling that now, in the 21st century, the hard lad of swinging 60s pop photography in Britain has found a niche for himself once more? Tempted back out of obscurity, Bailey is another vivid anachronism with which we keep falling in love. Like the past itself, he'll never really go away, and the photographs he and others take will forever be irrepressible links with human history. Maybe we say 'cheese', after all, because both aesthetics and Gruyeres need a little time to mature.