Martin Sharp, who died on Sunday at his home in Sydney's Bellevue Hill, was an influential artist, cartoonist, magazine and counterculture figure.

Sharp's art - bold, colourful, exuberant and distinctive - captured the counterculture of the 1960s and 1970s both in Australia and internationally.

Sharp's death at the age of 71 followed a long struggle with emphysema.

Wayne Tunnicliffe, head curator of Australian art at the Art Gallery of NSW, said on Monday Australia - and Sydney in particular - had lost an important artist and "an absolutely unique voice".

"He left the art gallery walls and went out there and really engaged with people," Tunnicliffe said.

Sharp was born in Sydney in 1942. After leaving the private Sydney boys' school Cranbrook (where he had an outstanding art teacher in Justin O'Brien), Sharp studied at the National Art School in East Sydney. He and fellow artist Garry Shead helped start an unofficial student newspaper there called The Arty Wild Oat.

He met Richard Walsh, who was editing University of Sydney's campus newspaper Honi Soit, and Richard Neville, who was editing the University of NSW's Tharunka.

The result was Oz, a self-proclaimed "magazine of dissent", first published in 1963. Sharp was art director and a major contributor to the magazine, which quickly developed a nationwide following.

The trio were twice charged with printing an obscene publication, courtesy of Sharp's poem The Word Flashed Around The Arms and the famous Oz cover in February 1964 that showed Neville and two friends pretending to urinate into a Tom Bass sculpture set into a wall of Sydney's P&O building.

Sharp, Neville and Walsh were tried, convicted and sentenced but, after public outcry, were acquitted on appeal.

They then headed to London to try their luck, launching the equally controversial London Oz, with Sharp once again coming up with a series of memorable covers and contributions.

Richard Neville told AAP on Monday: "Without Martin's talent I don't think Oz both in Australia and in London could have created the momentum it did."

One night, at a London nightclub called the Speakeasy, Sharp met musician Eric Clapton, and told him about a poem he'd written. The Cream guitarist turned Sharp's scribbled words into the lyrics of Tales of Brave Ulysses, which became the B-side of Strange Brew.

Sharp went on to design memorable album covers for Cream's Disraeli Gears and Wheels Of Fire albums.

He also designed iconic posters of artists including Bob Dylan, Donovan and Jimi Hendrix.

Shead said on Monday Sharp would be remembered primarily as a graphic artist, describing his work in that area as "revolutionary".

After returning to Australia in 1973, Sharp again showed his bold eye for design in a series of posters for Sydney's Nimrod Theatre and for Circus Oz.

He also established the Yellow House artists' collective in a terrace house in inner-Sydney's Potts Point.

Sharp commenced a series of missions - to help save Sydney's Luna Park, to champion the genius of US singer and ukulele player Tiny Tim, and to immortalise the "Eternity" man Arthur Stace.

Sharp used Stace's message in much of his art and was instrumental in the word "Eternity" lighting up the Sydney Harbour Bridge on New Year's Eve 2000.

Sharp was also outspoken in the causes of civil liberties and Aboriginal rights.

He once told Australia's Time Out magazine (for which he also designed a cover in 2007): "Art has been my way of having a say."

That view was echoed on Monday by Stuart Purves, director of the Australian Galleries in Sydney.

"Martin was one of those artists who is all artist," Purves said. "He was an artist from the day he was born to the day he died, and never veered off that path. Donald Friend would have said Martin was an artist the way a dog is a dog."

Purves recalled an exhibition Sharp had at the Australian Galleries during his Tiny Tim period, describing it as "the most circus-like, quality, great fun show".

"Martin just kept bringing works in - you couldn't see the walls in the end."

Shead, who visited Sharp weekly in the past couple of years as his health deteriorated, says he painted him for an Archibald Prize entry a couple of years ago because he feared he was dying.

Sharp never married and, according to Shead, his ramshackle Bellevue Hill home - which Sharp had inherited from his grandfather in his twenties - was always full of his art, friends and unfinished projects.

"He was still painting right to the end," Shead says. "He said, `I've still got too much to do'."

Shead described Sharp as "charismatic, with a lovely nature and a kind of astringent wit - he could put people in their place very quickly".

Neville said Sharp "covered the waterfront" both on the issues he took up, and in his art, which ranged from bright and poppy to "bitter" and acerbic.

Tunnicliffe paid tribute to Sharp as "a pop artist in the true sense", in that he engaged with popular subjects, worked extensively in things such as album and magazine covers and posters, and created work that was enjoyed "by a very broad audience".

"He really engaged with Sydney and Sydney culture - and then took it to the international stage."

Tunnicliffe said that after Sharp's return to Sydney in the 1970s, "he really engaged with the city, its people and really reminded us of our history and our beloved institutions".

Richard Neville described Sharp as "a wonderful friend".

As an artist, he said, Sharpe had been "an outsider but also an insider... At core he was an artist beyond repute in my opinion, but not an artist necessarily certified by the academy".