But now the foyer of the National Portrait Gallery has been tuned into a digital studio with artist Tony Curran using an i-pad to draw anyone who sits in a brown chair in front of him.

The interactive work will see Curran return every day for 33 days- Friday was day 24.

So far he has ‘‘completed’’ more than 140 portraits. The work As Long As You’re Here, is part of Curran’s PhD research.

‘‘I draw for as long as the person wants to sit...theoretically a portrait is never done, there is always more to do,’’ Curran said.

He said the most common question from his subjects was ‘‘Is it done?’’

‘‘It’s done when the subject says it’s done.’’

One subject who was still sitting when the gallery closed at 5pm returned the next morning wearing the same clothes to have the portrait ‘‘completed’’.

‘‘I’ve had people sit for as long as three hours or as short as five minutes,’’ Curran said.

About 70 per cent of the subjects have been women.

‘‘I think that reflects the gender divide at gallery audiences.’’

And it’s a bargain- at a recent Sydney exhibition Curran’s digital portraits were selling for $1650, while those attending the NPA are emailed a copy of the work for free.

Richard Miller, 63, from Brisbane visited the National Portrait Gallery on Thursday. The line for a portrait was too long so he returned the next morning.

‘‘It’s just serendipity... I’ve never had my portrait done and it will be wonderful for the kids,’’ Mr Miller said.

Curran started using his i-pad as easel, paints and brush about 18 months ago.

‘‘I was working on a portrait for someone in Sydney and I was living in Wagga Wagga- carrying around paints was impractical.’’

He said the juxtaposition of a dry portraiture and new forms of contemporary art intrigued him.

Curran is self-funding the project at the gallery. He finishes the work at 5pm on Sunday November 10, but will be at the gallery every day between 10am to 1pm and 2pm to 5pm until then.