What does the photography term ETTR mean?

ETTR = Expose to the Right: Expose to the right.

Expose to the right

Exposure to the right as much as possible (often called ETTR on the Internet, exposure to the right) is a technique used by photographers to create a RAW file that contains as much information as possible .

The technique is very simple—just use an exposure setting that allows the camera's sensor to register the maximum amount of light without overexposure. The result is that you get a histogram that is as close to the right as possible without going beyond the right limit.

The main benefit of exposing to the right is that it reduces the level of noise in your photo. And it also ensures that you get as much shadow detail as possible without losing any highlight detail.