Here's how I think it works: Fine Art AA is full scene supersampling. Normal AA is only supersampling pixels of the image that have a high contrast with the pixels next to them. The Fine Art AA also has a higher degree of supersampling (if you use settings of 16 or higher) When using noisy textures or high contrast textures Fine art is clearly better. I'll make a post tomorrow or maybe this evening to demonstrate it.

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