At the risk of compromising national security, Lens would like to present this nighttime view of the Jacob K. Javits Convention Center, taken on Tuesday by George Hahn, a 39-year-old Web site designer who lives nearby in Manhattan.

No, Mr. Hahn didn’t see the problem, either.

He had been watching construction progress on the northward expansion of the Javits Center. “As an architecture enthusiast,” Mr. Hahn said, “its angular design with slanted roofs, glass and corrugated metal make it look like a sexy modern garage, and I wanted to take a picture of it.”

As I stood at the open gate of the fenced-in parking lot at the southwest corner of West 40th Street and 11th Avenue, I started to aim my camera upward toward the building. Within seconds, an N.Y.C. taxi abruptly pulled in front of me. It was dark. There were rats. The cab startled me. ‘Can I help you?’ asked the driver in a tough tone. I then noticed the flashing red, white and blue lights in the cab’s grill. It was N.Y.P.D. in a taxi costume. ‘I’m taking photos.’ ‘Of what?’ ‘The new Javits building.’ ‘Why?’ ‘I like the building. Is that O.K.?’ ‘Not in here.’

“By ‘here,'” Mr. Hahn continued in an e-mail to Lens, “I’m presuming he meant the fenced-in lot, in which I was not standing, by the way. Both of my feet were firmly on the public sidewalk next to the gate.”

Mr. Hahn said the undercover police cruiser pulled into the lot, then pulled out next to him and simply idled there briefly while he was taking pictures. While the officer made no effort to stop him, Mr. Hahn said he was under the impression that an effort was being to made to intimidate him.

As far as such encounters go, Mr. Hahn’s brief run-in was fairly benign.

But his story and many more like it are becoming increasingly common as authorities seek — often against their own stated regulations — to smother photography in public places under the blanket of “security”; a rubric that exempts them from explaining how it is that pictures of cityscapes and landmarks that have been photographed thousands of times before are so threatening that they must be prohibited.

Jim Dwyer’s About New York column on Wednesday, “Picture This, and Risk Arrest,” concerned the arrest by the Amtrak police of Duane P. Kerzic, for taking pictures of a train pulling into Pennsylvania Station, and of Robert Taylor, by the New York Police Department, for taking pictures on a subway platform in the Bronx.

On Monday, in “Freedom of Photography: Police, Security Often Clamp Down Despite Public Right,” The Washington Post documented many instances in which photographers drawn to federal buildings, bridges, trains or airports have been treated as potential terrorists. In a sidebar, “Caught With a Camera,” The Post also published examples of 10 photographs that had drawn official interdiction.

Luke MacGregor/Reuters

In recent years, photographers in Britain faced even more onerous restrictions under the broad stop-and-search powers granted to the police under Section 44 of the Terrorism Act 2000. But this month, in response to a decision by the European Court of Human Rights, Theresa May, the home secretary, announced that the police would no longer be permitted to stop and search a person without reasonable suspicion.

“We are delighted at this news of the suspension of Section 44,” said a group called I’m a Photographer, Not a Terrorist. “We are sure photographers across the U.K. are looking forward to freely photographing in a public place without the being bullied by the police and corporate security guards.”

It sounds as if they’re leaving it up to us, now.