This is a 4k map with a few white and black lines drawn across it. I was testing bump maps in blender. The first map was sharper and I presumed that was causing these artifacts. So I despeckled it twice in photoshop but that did not work. I through in a few Gaussian blurs after that and together they only had a very minor effect.
I presume that there are minor variations in the tone of the black line that blender is picking up. I however am not sure how to stop it or get rid of it. This is zoomed in pretty far BTW and it does look good from far away and rendered at normal resolution. What you are seeing is a line drawn onto the surface of a sphere.
So… I presume that this is normal? And if I want to get rid of this I would need an even higher quality map?
I see in your screenshot those fateful letters - “.jpg.” That’s the problem, made worse every time you edit and recompress it. It’s probably not being compressed at a good ratio anyway - which would be 100. But even at 100 jpg used for bump is a terrible idea. Artifacts always show up in exactly those areas that would be the worst for bump - in borders between flat colors. Please use png! And don’t try to salvage the jpg with blurs etc, you just have to make a new one.