Dmitry Medvedev, the Russian prime minister, may have been the stand-in for Vladimir Putin, the newly re-elected president who snubbed the summit, but he seized the moment.
As photographers captured the pre-dinner scene, he gestured and joked animatedly about a series of pictures on the wall featuring Mr Obama with foreign dignitaries.
Seated in front of a wooden cabinet displaying ceramic plates and vases, the US president grinned broadly while Mr Cameron also smiled at the remark. The only woman present, Angela Merkel, the German chancellor who was wearing a pink jacket and white trousers, leaned in to add a comment.
Yoshihiko Noda, the Japanese prime minister, followed a translation of the exchange through an earpiece, but Mr Hollande and José Manuel Barroso, the European Commission president, both English speakers, left their audio devices unused on their plates.
The water glasses were already filled, but the food and wine were served in private later. Unusually for such occasions, the menu was not disclosed.
Notebooks and files were, however, conspicuously out on the table as the leaders prepared to chew over weighty fare of international politics, leaning into microphone boxes to make their points while aides listened from a nearby room.
Wearing an open-neck blue shirt, blue blazer and brown trousers, Mr Obama earlier greeted his guests individually outside the cabin.
"François, we said you could take off the tie!" he called as the French leader strode towards him.
"For my press!" riposted Mr Hollande as he grappled with the sartorial complexities of his new job.
Mr Cameron opted for a dark suit and open-necked shirt. "This is a nice, peaceful spot," he remarked politely of Camp David. "It's not bad," replied the president.
Mr Medvedev adopted the most casual look, wearing an electric-blue sports jacket and jeans. "This is my new place!" he joked, nodding to the lodge.
Angela Merkel, the German chancellor, whose austerity economics have left her increasingly isolated, was less upbeat, giving a non-committal shrug when Mr Obama asked how she was. "Well, you had a few things on your mind," he noted.
After dinner, a chocolate birthday cake was presented to Yoshihiko Noda, the Japanese prime minister who is 55 on Sunday.
Guests later bedded down in lodges that White House officials acknowledged were less than luxurious. In the eagerly-awaited cabin pecking order, Mr Cameron landed Maple, one of four "VIP guest" lodges. By contrast, Mr Barroso and Herman van Rompuy, the European Council president, shared a cabin.
Yesterday morning, Mr Cameron and Mr Obama engaged in "treadmill diplomacy" as they took to the gym before breakfast for a one-to-one session to discuss the eurozone crisis. Aides did not clarify whether they were also sending a message about their fitness to govern.