All magazines love them and newspapers use them to illustrate tricky features - they're library photos or stock shots. Models or actors are photographed in a variety of poses and situations, then photographic libraries or agencies sell on the rights to use the photographs.

The people in the photos effectively "sell" their image - usually for a one-off payment. The photographic library then owns the image and rents it out several times for use on a sliding scale of charges. The giveaway for the reader may be found in an inconspicuous caption, stating "posed by models".

There are several reasons why a stock shot might be used instead of a specially- commissioned one. Cost is one thing, they frequently work out less expensive - but another reason is sensitivity.

Sometimes, for example, an editor might find it too difficult to persuade an interviewee suffering from an embarrassing medical problem to agree to be photographed or to find an executive who would agree to be photographed to illustrate an article on executive stress - so they use a posed, anonymous shot instead.