快猫短视频

San Francisco

OLD-FASHIONED film cameras are better at catching bank robbers than modern
video cameras, according to an FBI report presented at the American Academy of
Forensic Sciences. Bureau scientists say video cameras can be useless for
identifying criminals.

In the early days of surveillance, banks had hidden film cameras that were
triggered by staff during a crime and snapped photos every few seconds. But in
the 1970s, many banks switched to video cameras, believing that it was important
to be able to monitor an area continuously鈥攁nd to cut the cost of using
film.

Now most banks use video. 鈥淲e鈥檙e seeing so much more video than we do film,鈥�
says Thomas Musheno, a forensic scientist at the FBI laboratory in Washington
DC. The problem, he explains, is that the FBI usually uses tiny details they
call 鈥渦nique identifying characteristics鈥�, such as scars or moles, to identify a
criminal.

In close-up, video can capture these features as well as film. But cameras
are often mounted 6 metres from tellers. At that distance, an image of a
gunman鈥檚 face can be decidedly uninformative. 鈥淵ou can hardly tell it鈥檚 human,鈥�
says Musheno.

The cameras normally record a picture field once a second鈥攎aking a
2-hour tape last for 72 hours. Only every second line of the 480 lines on the
screen is recorded in each field. So if a distinctive wart or scar lies in the
odd lines, the police are out of luck.