When two high-ranking army officials asked artist and gallerist Terence Teo to collaborate on an exhibition to celebrate 50 years of national service (NS), he was keen, but had concerns.

"Artists like to draw what they feel like drawing and creating. I told the two officials, I have one condition - don't ask our artists to produce a poster," says Teo with a laugh.

Their response? "'No restriction. As long as you see something you like, you draw.' It was very freeing," says the 64-year-old president of the Singapore Art Society.

The resulting exhibition, titled Commemorating NS50 Through Art, comprises about 140 artworks by 53 artists that pay tribute to NS in different ways.

About 80 of the works will be shown at Suntec Singapore Convention & Exhibition Centre from July 30 to Aug 13. Admission to the exhibition is free.

The other works were displayed earlier at Ion Art Gallery and The Arts House.

About 80 per cent of the works that will be displayed at Suntec were not shown at the other two venues.

The artists, whose ages range from late 30s to 85, are members of the Singapore Art Society, which was established in 1949 to encourage the practice and understanding of art. They include Teo and Cultural Medallion winners Goh Beng Kwan, 80, and Ang Ah Tee, 74.

The works span different mediums, from watercolours depicting army uniforms being hung out to dry, to calligraphic renderings of the word "courage", to an oil painting of one of the Navy's amphibious vessels.

Artist P. Gnana, 47, for instance used materials such as a camouflage pattern cap and bits of gunny sack in his collage work, titled Fearless Protector, to depict an anonymous soldier.

For the exhibition, the artists visited about 20 camps and units of the Singapore Armed Forces and Home Team agencies over four months to observe their activities and do on-site sketches.

Exhibition curator Woo Fook Wah, 60, says: "It was very inspiring because this was the first time artists were given access to these facilities and we could talk to the people. They also did demonstrations - for example, the military police put up a motorbike show for us and took us to see their dogs. It was enjoyable."

All the works are on sale, with prices ranging from $800 to $70,000. Between 12 and 18 works have been sold so far.

The most expensive work was done by 83-year-old artist Chieu Shuey Fook. His 1.22 by 1.55m coloured metal relief work depicts different scenes in a young soldier's journey through NS.

Calligrapher Goh Yau Kee, 68, created three works, each depicting the words "bravery" and "courage" in Chinese.

He initially had some concerns about the NS theme .

"Calligraphy is not like a painting. You could paint a tank or a soldier. But for calligraphy, how do you do that?," he says. "Normally, I do calligraphy in a more traditional way. For this exhibition, I added some more creative elements."

His work that will be shown at Suntec has one of the characters flipped so that the form of the words resembles that of a mother and a child.

Mr Teo adds with a laugh: "Normally, he may not dare to write this way. But after visiting the camps, he dares to do so."