Ranging from images of sharp industrial lines and hoar frost ice flakes to those of trees and the human body, about 60 photographs depicting the exhibition's line theme are on show at the gallery in the Central Stories Museum.
Museum exhibition technician Luke Anthony said it was the second show since a new format had been adopted, which included framing the photos and charging an entry fee.
The new format and the theme, which "wasn't particularly limiting", might have been why they had so many entries, he said.
Guest judge Eric Schusser, who has some of his own work in the exhibition, said he was "very, very impressed" with the quality of the work and it was hard to choose the top three.
A fan of black and white photography, he said it was great to see so many people choosing that style.
While judging the photos on Wednesday ahead of the exhibition opening, he said he was looking for "something a bit different, something technically good or perhaps something with a bit of emotion rolled into it ... something a little bit extra than just lines".
He awarded first prize to Tom Lamb for his photo titled Triangle - a black and white industrial-type image with ladders, angles and shadows.
Dunstan High School pupil Matthew Arnott (17) won second prize with his triptych, Lines of Field - a combination of three images of grass or flax.
Third prize went to Colin Verry for his image of the gates at the Clyde dam with mist in the background.
The people's choice award is still to be decided - a voting box is in place at the gallery and once the show ends, on September 16, the votes will be tallied and the winner announced.
