Event Horizon Telescope. Black Hole Sagittarius A* (2019). Retrieved from: https://news.harvard.edu/gazette/story/2019/04/harvard-scientists-lead-team-revealing-black-hole/

"But there is one point I want to draw your attention to: there is always some ambiguity in what the true image is. [...] For the EHT, the data we take only tells us only a piece of the story, as there are an infinite number of possible images that are perfectly consistent with the data we measure. But not all images are created equal— some look more like what we think of as images than others. To choose the best image, we essentially take all of the infinite images that explain our telescope measurements, and rank them by how reasonable they look.  We then choose the image (or set of images) that looks most reasonable.“
- Event Horizon Telescope. https://eventhorizontelescope.org/science