PLAYING up in Sydney's CBD just became harder.

The city's network of 82 surveillance cameras now not only track your every move but can zoom in on the minutia of life like never before, even in low-light.

The vast boost in capability means every step on the 4km walk from one end of the CBD to the other - The Rocks to Surry Hills - can be tracked by cameras, with the footage kept for 28 days.

The $3.5 million revamp comes as the Sydney City Council made the switch from video technology to digital, allowing sharper images and greater storage capacity.

With that came a quadrupling in the size of the network's control room hidden in the bowels of the council's complex on Kent St.

A bank of 16 massive flat screens line one wall, with six camera operators watching the country's largest city in action 24-hours a day.

It's a far cry from the old room that housed two operators watching four screens.

"We now have most of the city covered," council's acting chief executive officer Garry Harding said yesterday.

"We cover all of Oxford St and up to Kings Cross and we've extended into Glebe. If there's any criminal activity in a street in the city, there's a fairly good chance that activity will be recorded."

Raj Masson, who helped create the new system, said the cameras were now so good they easily tracked the waves of people surging from all parts of the city to The Rocks for the New Year's Eve fireworks.

Mr Masson said the council's system was equipped to one day be able to run smart technology such as facial recognition and crowd counters.

A council spokesman said there were no immediate plans for further expansion.

The cameras have become an essential tool for the city's police, with the live feeds now being used almost every day to track possible criminal activity.

Council security staff monitor the cameras.

When they spot possible criminal activity the feeds are sent through to police, who can watch and guide officers to the scene but not record.

City Central crime manager Detective Chief Inspector Jon Alt said the technology was "integral to everything we do these days".

"When we are trying to work out what happened (at a scene) they can play back the footage for us," he said.

"They have been very successful in resolving a number of matters and our prosecution rate is higher as a result."

The move to digital recording also means a faster replay of what occurred before police arrived, making it the equivalent of the video umpire in cricket.

Civil liberty and privacy concerns have resulted in tight controls of the captured footage, with the council even refusing to allow captured images to be used for publicity purposes.

Access to the control room itself is controlled through four doors which need electronic swipe cards to be opened.