Mind you, that's a JPG you are editing, so in the 8 bit sRGB color space. That means manipulations can lead to errors and illusions due to the color space being

Mind you, that's a JPG you are editing, so in the 8 bit sRGB color space. That means manipulations can lead to errors and illusions due to the color space being non-linear and clipped[0]. The original data was likely linear and at a much higher precision. If the source was a 16 bit linear grayscale PNG for example you could be much more assured you're not seeing the effects of JPG compression and things that were actually measured. EDIT: Found better sources: 16-bit sRGB PNG: https://eventhorizontelescope.org/files/eht/files/20190410-78m-4000x2330.png?m=1554877782 https://eventhorizontelescope.org/files/eht/files/20190410-7... 180 MiB original TIFF: https://www.eso.org/public/images/eso1907a/ https://www.eso.org/public/images/eso1907a/ [0] https://www.youtube.com/watch?v=LKnqECcg6Gw https://www.youtube.com/watch?v=LKnqECcg6Gw