Pamela Rosenberg confirms that San Francisco Opera budget cuts played a big role in her leaving the company. A smaller budget means fewer new productions. “That part of the job has always been my most creative — being a midwife to artists and projects, and getting new productions conceived and done,” Rosenberg explained Thursday in a phone call from her office in the War Memorial Opera House. It looks like I won’t be able to do that in the future — we’re taking the budget down by 20 percent, and that will mean we will have the means to do a maximum of one new production a year for at least the next three seasons. At this point in my career, that’s just not enough for me.”