They would rather not talk about it, but umpires may be just as star-struck as the average baseball fan.

Two researchers looked at photographic evidence and found that umpires make more errors in favor of All-Star pitchers than in favor of pitchers who have never been to an All-Star Game — about 17 percent more.

This is a subject umpires are naturally hesitant to discuss.

“I don’t know the science,” Fieldin Culbreth said as he prepared for a game between the Mets and the Athletics. “And I wouldn’t understand it even if you tried to explain it to me. I umpire from here and here,” he said, indicating his head and his heart.

Mets starter Jon Niese was more sympathetic than shocked. “It’s still a human back there,” he said, “so they make mistakes.” He paused for a beat. “But if you’re going to give anyone the benefit of the doubt,” he added, “it’s going to be somebody like Adam Wainwright.”

But the science exists, for anyone who wants to look at it. Every major league stadium is equipped with the Pitch f/x system, which includes strategically placed cameras that record the locations and trajectories of every pitch.

The technology provides a record that is difficult to dispute. In the seasons the study covered — 2008 and 2009 — umpires earned a B-plus average, at best, in calling balls and strikes.

The researchers —business school professors Jerry W. Kim of Columbia and Brayden G. King of Northwestern — looked at data on 756,848 pitches over 313,774 at-bats in 4,914 games. Some umpires were, unsurprisingly, more accurate than others, but on average they called a strike on 18.8 percent of pitches that were actually out of the strike zone and a ball on 12.9 percent of pitches that were, in fact, strikes. And for each additional appearance in an All-Star Game there was a 4.8 percent increase in probability that an actual ball would be called a strike.