SUMMARY In the WebP export, the tooltip for ‘Target PSNR’ says: If non-zero, specifies the minimal distortion to try to achieve. Takes precedence over Target Size. I’m not *sure* this is wrong, but I can’t get it to make sense. Why would one set a target *minimal* distortion? Shouldn’t this be either the *maximal* distortion or the average distortion or something like that? STEPS TO REPRODUCE 1. File → Save As … → WebP image → Advanced. 2. Hover over the ‘Target PSNR’ input field.
Not a bug. This is the official description of the parameter, as taken from the WebP API. The URL has been attached for future reference.