By Neil Smith
BBC News Online
A new exhibition of photographs, which opens at the Hayward Gallery on London's South Bank on 24 June, suggests that digital manipulation of images has effectively killed the portrait.
Pop star Michael Jackson is one of several celebrities featured
They say the camera never lies, but recent examples of photographic trickery prove that is anything but true.
GQ magazine was criticised for "touching up" a cover shot of actress Kate Winslet, while a photograph that showed US presidential candidate John Kerry sharing a podium with Hollywood activist Jane Fonda was found to be a forgery.
Now a new exhibition highlights the full range of devices a photographer can use to alter, reshape and transform the human face.
About Face: Photography and the Death of the Portrait presents around 100 works by over 70 artists and photographers who have turned to the face as subject matter.
William A Ewing, curator of the exhibition, says he hopes to provoke a lively debate on what now constitutes photographic truth.
"We noticed how genetic engineering, the phenomenal rise in cosmetic surgery, and the computer revolution where faces can be adapted and doctored, all seemed to be converging in a fascinating way," he told BBC News Online.
Ewing, director of Musee de l'Elysee in Lausanne, Switzerland, also seeks to challenge the idea that a photographic portrait can offer "a window on the soul" of the subject.
One of the more controversial images on display at the exhibition
"The idea that a portrait reveals the soul is a very tenacious idea, but it's very difficult to defend," he explains.
"Doubt pervades, especially when the computer makes that doubting so much easier."
Divided into six sections, the works on display range from giant-scale colour photographs and photo montages to grainy mug shots and complex computer manipulations.
Some of the images offer alternate versions of reality: for instance, what the Queen or Arnold Schwarzenegger would look like if they were black.
Other, more controversial photographs show faces stripped of their features - what might happen, Ewing suggests, if genetic experimentation is allowed to continue unchecked.
There is also a photograph of a Kurdish asylum seeker who sewed his lips and eyelids together as a protest against his deportation from the UK.
Czech artist Jiri David superimposed his own tears on Tony Blair's face
This disturbing image is one of several works that pass comment on political issues, often through humour or satire.
In his series No compassion, artist Jiri David superimposes his own tears on agency photographs of world leaders, including British Prime Minister Tony Blair.
"Faces we rarely see displaying emotion now exude an artificial compassion," explains Ewing.
Another composite portrait depicts the leaders of the superpowers involved in the nuclear arms race in the 1980s - US President Ronald Reagan, Soviet premier Leonid Brezhnev and British PM Margaret Thatcher, among others.
The twist is that the proportion of the leaders' faces used is in direct proportion to their respective country's nuclear arsenal.
Elsewhere, the idea that a single image can present an accurate representation of a sitter's identity is questioned by serial images of the same face photographed over a period of time.
These include portraits of a young mother taken a few weeks, then a few months after giving birth, and a series of identically-posed passport photos that chart the artist's life over a number of years.
Alison Jackson used look-alikes to imagine a royal argument
The pervasive influence of celebrity on our culture is reflected by photographs of pop stars Michael Jackson and Bjork and a provocative shot of a young boy made up to resemble Madonna.
But the exhibition also includes "found images" of pedestrians in New York's Times Square captured without their knowledge, or newborn babies snapped moments after their birth.
"Every day we look at thousands of faces," says Ewing. "So we said, let's look at the face."
Those who visit this exhibition may find themselves never looking at a face the same way again.
About Face: Photography and the Death of the Portrait runs from 24 June to 5 September.