IT could be a multi-millionaire's mansion on the Peak; the Jockey Club wanting to check out the construction progress of its latest clinic; or Hong Kong Land wanting to show off its impressive property holdings in its annual report - what better way to catch these images than from the air. ''Yes, we get the occasional individual who wants us to take to the skies for a photograph of his Peak mansion to show to his friends,'' said Kasyan Bartlett, director of Airphoto International. ''But most of the time it's company work; engineers, property agents, construction and property companies wanting to locate sites, check on building progress and get shots for their annual reports.'' Airphoto International was born out of the work of Mr Bartlett's father, Magnus, with Over Hong Kong, which during its on-and-off 10-year existence has documented the ever-changing topography and skyline of Hong Kong from the air. Each new edition climbs to the top-selling list as quickly as Kasyan Bartlett and his Heliservices pilots take to the skies over the territory. ''It was the construction, agents and building companies that came to us when they realised what sort of service we could offer,'' Mr Bartlett said. He and his assistant, Wong Chun-wai, take the photographs. They also take photographs for Over Hong Kong. Even though total costs can approach $10,000 an hour to hire a helicopter, Mr Bartlett maintains that aerial photography is more cost-effective than ground photography. ''It costs $8,940 per hour to take a client up with us, but if we are doing work for say, the Sai Kung District Board, we could cover it in half an hour. It would take a land photographer a week to do the same job and you would not get the same perspective,'' Mr Bartlett said. He said he always tried to maintain the highest quality photography even if it involved just taking a picture of a landfill or construction site. ''This is especially so in the case of annual reports, even to the point of taking the photograph at the same time of day from the same angle. ''A lot of the flights are early morning because that's when we can get the best light,'' he added. Because of the work of Airphoto International, the company had built up an impressive library of work, which Mr Bartlett claimed was used constantly as a source of reference by companies involved in construction and infrastructure work. ''The thing about Hong Kong is, because it changes so quickly, a two-year-old photograph can become historical. Our library contains about 20,000 photographs,'' he said. Mr Bartlett said June and July were the best months for flying because of the clearer weather, while February, March and October also offered opportunities to ''get out on the skids and have some fun''.