The retired umpire, who quit prematurely after some bloopers by him in the just-concluded India-West Indies series drew criticism from India captain Mahendra Singh Dhoni, said technology is hard to rely on.
"When a batsman plays a shot well away from his body, and you as an umpire see the ball strike a glove, go through to the keeper, and you hear the sound, you can draw no other conclusion than it has been gloved to the keeper and the batsman is out," Harper told `ESPNcricinfo`.
"That it can`t be confirmed by a camera at 25 frames per second, that`s technology`s problem. If they were filming at 1800 frames per second, like those super slow-mos, you`d see the glove depressed with the contact from the ball," he added.
Harper explained the intricacies of the technology that is used right now and how it is insufficient to reach a conclusively correct decision.
"At 50 frames per second there is a very slim chance of the ball ever being captured making contact with the pitch when it actually lands, because there is a minimum of 60cm (of the ball travelling) between frames," Harper said.
"If the cameras cannot capture the ball touching the pitch, I`m not quite sure how they can claim the degree of accuracy they do claim.
"So the more advanced technology becomes -- unfortunately it is more expensive -- the more likely the technology will be of a positive assistance to the game. At the moment it is not the aid that I believe it is claimed to be," he added.