Excuse me, what is the photographer doing, taking 3D photos, and what is in his left hand? (see photo)

It looks like a fake 3D camera. Both cameras are connected with cable release, and the external shutter is in hand, which ensures that the two cameras trigger the shutter completely at the same time.

The photos taken in this way correspond to the left and right eyes respectively, but they are also stored in two cameras respectively. They need to be copied to the computer and processed by special software to generate 3D.

Theoretically, the effect is exactly the same as that of a dual-lens 3D camera.

Finally, the photographer in the picture holds the shutter in his right hand.