Hi guys, have this little issue with a bump map, very simple black and white contrast. But shows some dots artifacts…
Color space is non-color, changed it to filmic log and it’s better but still not right.
Here is the map I’m using:
And this is the render:
I tried changing some parameters but no luck
You need to use at least 16Bit images and lossless compression as bump.
Hi, so basically I need to export that map from photoshop as 16bit and lossless compression ? as png ? jpeg ?
thank you 
Jpg is not lossless compression, you have to use png.
Yes, it works, thanks a lot
A bump map creates shadows by looking at the difference in brightness between adjacent pixels. The thing is that it doesn’t care how much of a difference in brightness there is, whether it’s between black and white, or black and very dark grey, it will give the same output. That means that the jpeg compression causes very slight changes in brightness which you can’t see with the eye, but which are picked up by the bump map.
This is what the bump map looks like when you turn the brightness up:
To fix it, you can just use a lossless format like png or tiff (it doesn’t necessarily have to be 16bit).
Thanks for the explanation ! makes sense.
What if I want a slight gradient in the map ? can I do that in blender ? or do I have to fix that in photoshop, there are too many lines to add a gradient to every lines.
thank you again
Sure it does. Maybe not so visible in this particular example but you’ll definitely notice in fine gradients.
In general, most of data maps give best quality when at least in 16Bit.
It just depends on the map and what you’re using it for. If it’s just for detailing like this, then often using 16bit is just a waste of memory. If there are big gradients, though, it is worth it.
I sometimes use OpenEXR DWAB compression, really small file size for high Bits
