Peter Keresztury is an art show producer who has noticed a recent trend: bondage.

The creator of “On the Edge 4,” an erotic photography show and sale this weekend at SOMArts Cultural Center, says when “50 Shades of Grey” hit the best-seller list, awareness and interest in bondage and fetish increased.

“It’s getting to be more and more mainstream,” Keresztury says. “But before ‘50 Shades’ there was Marquis de Sade.”

Keresztury co-produces “On the Edge 4” with his wife, Deborah, who is also his business partner at Erotic Entertainment. Keresztury says the fourth annual show is, to his knowledge, the largest erotic photography show in the country, and perfect entertainment for Valentine’s Day.

Twenty-six artists, including Keresztury, are exhibiting about 450 photographs at the three-day event, which also features a pole dancing performance and a lingerie fashion show Friday night, and corset and fetish wear fashion shows Saturday night.

While bondage has been a popular topic in “On the Edge” works, Keresztury says the show also offers “some nice fine art nudes too, displaying the beautiful female body.”

He adds: “It’s a mix. I ask the photographers to show the full range of their work.”

“On the Edge” exhibits boudoir and soft erotica, hardcore and everything between.

Keresztury, who focuses on fine art nudes in his own photography, admits that digital advancements and Photoshop have made the art form more accessible than it used to be.

“I remember going in the dark room and developing and trying to do light manipulation in the dark room,” Keresztury says. “It’s so easy now with digital. I think as soon as the camera and film was developed, they were taking pictures of nudes — that was definitely one of the first things.”

Keeping in mind that the erotic category may not be for everyone, Keresztury notes that “On the Edge 4” has a disclaimer and warning posted outside the venue. At the same time, he says, “It’s going to be a wonderful experience for first-time viewers.”

IF YOU GO

On the Edge 4

Presented by Erotic Entertainment

Where: SOMArts Cultural Center, 934 Brannan St., S.F.

When: 4 to 9 p.m. Friday, 1 to 9 p.m. Saturday, noon to 5 p.m. Sunday

Admission: $10

Contact: (415) 863-1414, www.eroticartevents.comArt & MuseumsartsDeborah KereszturyErotic photographyOn the Edge 4