You know that San Francisco Ballet is going to offer something exciting if the standing-room crowd is four deep. That’s not an unusual occurrence. And you can bet a pair of tickets that the standees will shout the loudest “bravos” for a cheeky new ballet from Mark Morris, or an exquisite performance from principal dancer Tina LeBlanc. San Francisco Ballet dancers can perform anything. Each season programs run the gamut from full-length classics, including “Nutcracker,” Swan Lake” or “Giselle,” to something lyrical from Jerome Robbins and something quirky and contemporary from Morris, William Forsythe or Christopher Wheeldon. Artistic director Helgi Tomasson brings European elegance and Balanchine rigor to America’s oldest ballet company. He trained in Europe and for many years was a leading dancer with Balanchine’s New York City Ballet. He’s credited with transforming San Francisco Ballet from a regional troupe into a world-class company. He’s known for giving young dancers from the corps de ballet the chance to perform solo roles, and for tapping principal dancers to choreograph new works. So when the great gold curtain sweeps up at the Opera House, you can count on something beautiful, engaging and even ravishing.