"Calendar Girls" is based on the 2003 film inspired by the true story of a group of middle-age, respectable Yorkshire women who posed nude for their Women's Institute calendar. At the end of the first act of this play, which opened Thursday night at the Underground, six women strike their provocative poses for pictorial posterity.

Each "shot" in turn was applauded warmly and loudly by the audience, because these actresses were doing more than acting at that point. They really were standing there nude on stage with strategically placed props. This is as real as it gets, so you have to applaud the commitment.

But there was also a great sense of fun and joy to be applauded as well. We are reminded repeatedly that these women are "nude," not "naked," which put what they were doing in the grand tradition of 1950s pin-up model Betty Page.

The pivotal pair are Kathy Laakso as Annie and Christine Winkler Johnson as Chris, best buds at the W.I. But while the ladies are having fun with their own version of tai chi and other activities, Annie's husband, John (Joe Meichsner), slowly succumbs to cancer.

His final words introduce the show's master metaphor of the sunflower. The pairs of giant sunflowers framing the set look like giant eyes, watching the watchers, as it were.

Chris comes up with the idea for a W.I. calendar that is not about Yorkshire churches or bridges, and then it is just a matter of convincing the kaboodle to drop their kits.

Yes, for some of the ladies, the calendar shoot is something of a lark. But for most of them, it is a question of overcoming deeply personal issues regarding grief, age and body image.

Celia (Emily Lanik Parr), the trophy wife, finds "flaunting it" is fun, while as Jessie the ex-school teacher, Celine Karich delivers a spirited denunciation of age discrimination with a great payoff line.

The most reticent members of the sextet are Cora (Shey Peterson), who is a single mother, vicar's daughter and church organist - not necessarily in that order - and Ruth (Cathy Berggren), who confronts a limit to her endlessly enthusiastic participation in W.I. activities.

The second act is simply not as much fun, but then, how could it be after that first act finale? There is a trio of speeches that earns applause, but the personal rift that develops just leaves something of a bad taste; after that photo shoot, we do not want to root against any of these women for a single moment.

Fortunately, director Rob Hadaway stages the scenes where the ladies read aloud the letters they receive, and the play's last letter, to heighten their emotional impacts and provide the requisite happy ending.

There is an actual calendar for sale of all of the actresses in the "Calendar Girls" cast - I would have complained most bitterly if there were not - with all proceeds being donated to the Solvay Hospice House. Even if you do not get to see the show (it was sold out before it opened) you can still get your hands on a calendar.

If you go

What: "Calendar Girls"

When: 7:30 p.m. Thursday-Saturday through Jan. 20; 2 p.m. Sunday, Jan. 21

Where: The Underground, 506 W. Michigan St.

Tickets: The run of the show is sold out. Standby tickets, $20 adults, $18 students, might be available at the door. More information at www.duluthplayhouse.org.