National ID card plan faces flaw

By Clive Cookson

A “fundamental flaw” in the government’s proposed ID cards and photo surveillance systems is the difficulty both people and computers have in recognising faces from photographs, the BA Festival of Science in York heard yesterday.

“This routine task, performed hundreds of times every day by passport officers, security guards and police officers turns out to be highly error-prone,” said Rob Jenkins, a psychologist studying the problem at Glasgow University.

Dr Jenkins and colleagues have come up with a technical solution - combining a dozen images of one individual to produce an “average” face that is far easier to recognise than any single photo - that could help the authorities in specific cases. But implementing this on a mass scale would be extremely expensive and controversial.

The researchers worked on the principle that it is much easier to recognise familiar than unfamiliar faces in a photograph. “To model increased exposure, we collected several different images of each person and averaged them to make a single image for each face,” said Dr Jenkins.

Averaging photographs is relatively straightforward with up-to-date image-processing software. Only a dozen photos were required to stabilise the image, with any extra images after that making little difference. Dr Jenkins said: “The resulting images are quite uncanny, seeming to bring out the true essence of each face.” The Glasgow team then checked averaged faces against the individual faces from which they were made. Both humans and machines were far better at recognising the average picture.

“This is because the averaging process washes out aspects of the image that are unhelpful, such as lighting effects, while consolidating aspects of the image that are diagnostic of identity, such as the physical structure of the face,” said Dr Jenkins.

“This boost in face recognition accuracy has major implications for crime prevention and national security policies. It also demonstrates that with face recognition, as with so many other problems, we can improve machine performance by mimicking nature’s solution.”

With the national identity card scheme expected to start in 2009, the breakthrough in better-than-photo recognition accuracy raises the question of whether face databases and ID documents should contain identityaverages, rather than standard photographs. In practice, this would be difficult to achieve, Dr Jenkins conceded. “Is there a willingness among the population to do this? I doubt it,” he said. “Imagine having to submit a dozen pictures from your photo album with your passport application.”

As far as passports and ID cards are concerned, the authorities will just have to live with their limitations - and not rely too much on photos to identify people.

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