While the debate rages on about the Decision Review System (DRS), the creators of Hot Spot and Virtual Eye, two of the systems that will be used to help the umpires deliver decisions, have spoken candidly on ESPNcricinfo's fortnightly audio show, Time Out, about the limitations of the technologies currently available.

"I don't think it is 100 per cent," Warren Brennan, the chief executive of BBG Sports, the Australian firm providing Hot Spot, said. Hot Spot is a thermal-imaging technology that helps detect edges and is now mandatory for DRS. The problems the system faces, Brennan said, are the impact on gloves and certain light conditions late in the day.

Ian Taylor, the chief executive of Virtual Eye, the ball-tracking system that was used to judge leg-before decisions during the Ashes in Australia, said that the challenge is to take the technology to a level that leaves no doubt. "Our job is to take the technology to a level where the umpires never need to doubt us, and if they do that's fine, we haven't got there yet."

The DRS was hotly debated at the ICC's annual conference in Hong Kong recently but the compromise over how to use it has thrown up more questions than answers, with cricket's governing body and the BCCI agreeing to two separate parameters for implementing the system and lingering doubts over 100 per cent accuracy.

Hot Spot was the one tool the BCCI insisted had to be part of the system but it, too, is not foolproof. "Things off the glove can be a bit hit and miss," Brennan said. "There is padding on the gloves, which is obviously quite soft and other parts of the glove probably have some metal, usually on the side of the fingers. We get different heat impressions from the glove. While the metal can heat up, it'll be quite hot and when the ball strikes the soft part of the glove, it doesn't leave a great heat signature."

Other situations include a "solar flare", which might happen when the sun is low and the bat turns in a manner like it's putting a mirror to it, or a "motion blur", where "an object in the picture is moving faster than anything else in the frame.

"We saw that in England recently with [Tharanga] Paranavitana. We were certain he got a very faint edge but because the bat was swinging through quite quickly, the picture was blurry for several frames until the bat slowed down and stopped and then it was quite obvious to us."

However, Brennan said the technology achieved a 90% to 95% success rate in most conditions. "The one time we had brought the Hot Spot to the subcontinent, we found that because there aren't clearer skies, a lot of the time it is quite hazy, we got perfect results."

Hot Spot will be used in the India-England series, and with more advanced technology. "We've just finished two new cameras. These cameras are with much faster frame rates and much better optics and I'm confident that at Lord's we'll get significantly better performance than our older cameras."

Ball-tracking has been downgraded to an optional part of the DRS and Virtual Eye's Taylor said while many apprehensions about its reliability were valid, they could be alleviated by investing in more advanced technology.

"In the early days, when it was proposed for decision reviews and predictive ball paths, we were quite open to say that we weren't confident that the technology was at that level," he said. "So, when they decided to go ahead with the DRS, we decided that we'll invest hugely to improve the quality of the tracking. The normal tracking speed was about 100 frames per second, but we spent a lot of time, effort and money to shifting that to 230-250 frames per second, so that we got more information for the computer to work with.

"We think there are solutions. We are confident that the higher you shift that rate, the better the decisions can be. I don't think at the Ashes [where Virtual Eye was used], at 230 frames per second, there was a single incident where we didn't see the ball on the pads for at least two frames (two of those 230 frames)."

Ball-tracking technology can't depend on TV cameras, as happened during the recent World Cup though. "At the most that'll be tracking at 50 frames per second," Taylor said. "We've got some pictures where, in that instance, the camera doesn't even see the ball hit the ground, let alone necessarily hit the pad. If the distance is short, the chances are that if you've got a low rate of frames, you won't get any records past the bounce. So the faster the frame rate is, the more chance you've got of picking two, three or maybe four frames that say 'after the bounce, this is where the ball went'. "So that's why we've been focussed on the 230 frames." (Click here to view a comparison of tracking using different frame rates.)

Predictions, even at 160 frames per second, Taylor said, were difficult to make with fast bowlers pitching the ball close to the pads. Hence the need to invest in more advanced technology. "Our goal should be to remove all doubt and until we've removed the doubts from the players, it's fair that they don't use it."