A caption written under a photo rather than across it keeps the picture intact and stays readable whatever the image is doing.
Text placed on top of a photograph has to survive whatever is underneath it, and photographs are rarely a uniform colour. A caption on a solid band is legible every time, without outlines or shadows fighting the image.
Captions carry information that the picture cannot: a name, a date, a place, an attribution. That makes them worth reading, which makes legibility more important than style.
Match the band to the image rather than defaulting to white. A dark band under a dark photo looks considered, while a white strip under a night scene looks like a mistake.
Below, on a band, if you want it read. On the image if you want it to look like part of the picture.
No.
No.