Muhammad Usman, 72, is a reservoir of knowledge on the history of photography in Kabul, and the elder brother of Asad Ullah. Here's a photograph of the two brothers outside Assad Ullah's photo shop in Kabul. Muhammad Usman is holding a picture of their father Muhammad Aman, one of the old school of photographers in the city.

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The black and white image of his father, shown close-up on the left, is one of the few personal photographs he possesses. Like many photographers, his life was thrown upside down from the years of war in Afghanistan.

"Everything was destroyed and looted in the [civil] war," he says "one room full of cameras - gone. I used to boil the water in the bucket but had no cup to drink the tea out of. I had no floor to sleep on for two years."

But he also remembers the peaceful times.

Muhammad used to work alongside his father in their photo studio in his younger days; and he reels off lists of students they taught together - Nasar, Hussein, Taori - most of whom he says have passed away; or those his father taught before his time, like Baba Sher and Abdul Samad, the father of Abdul Satar.

Muhammad also recalls with ease a wealth of knowledge on old photographic techniques such as the process of pasting gelatin on a glass-plate; and he has a story of where the kamra-e-faoree originally comes from.

As we interviewed Muhammad Usman in the backroom of his son's photo shop, where he spends his days helping out but no longer taking photographs because of his weakening eyes, a young man at the side interjected to tell us something, just in case we didn't realise, a fact we really should know: "He's a master photographer, you know, a master!"