Two walkers stranded in the Brecon Beacons in blizzard conditions used the flash on their camera to help alert rescuers to their position.
It took more than two hours to locate the walkers on Pen y Fan
The man and woman, from Cardiff, had gone for a "winter walk" without a torch, map or a compass, said rescuers.
They spoke to the rescue controller on a mobile phone, who advised them to use its camera flash every few minutes.
The pair, found near the summit of Pen-y-Fan on Thursday were described as "very cold" but unharmed.
About 40 members of Central Beacons and Brecon Mountain Rescue teams helped locate them.
Peter Howells, team leader said they were alerted at 1830 GMT to an area near Merthyr Tydfil known as the Neuadd Valley.
Some members of the team scaled the summit of Pen y Fan, which was in two foot of snow, looking for the pair but they were eventually found near the top at about 2100 GMT.
'A little embarrassed'
Mr Howells said incident controller Penny Brockman had earlier spoken to the man and woman on a mobile phone to try and pin-point their location.
"During breaks in the snow storm, Penny asked the pair to use the flash on their camera once every 15 minutes to help rescuers pin-point their position," he said.
"They were eventually found near the top of Pen y Fan. They both walked off the hill but were very cold and a little embarrassed."
A search and rescue dog was also used in the hunt for the man, 29, and the woman, aged in her mid-30s.
Mr Howells added: "They had gone out for a winter walk, but didn't allow sufficient time, did not have a torch, map or a compass, but they knew the area because they had walked it before."
The latest mountain rescue comes just days after among a group of nine people, including children aged two, three and five, were airlifted to safety off Snowdon.
Seven people from Liverpool and two students from Cardiff were taken by helicopter to Ysbyty Gwynedd in Bangor.