Yes, I think I've found in the past that even full colour formats seem to only produce 256 steps in Vue. Maybe vue converts them, or maybe at 16 million you still only have 256 brightness levels, I don't know. I presume you are not using the jpg format - as this will show compression artifacts. I'll have a fiddle tonight, its worth looking in to. Several times in the past I've done stuff like this with loads of resoultion and colour levels, only to get various forms of step effect in Vue.