Magic Find has no effect on rune drops. Player settings will increase rune drops at players 3, 5, and 7.
A good way to explain it is that when an item drop happens, the game rolls on which item drops. After that, it rolls on the quality of the item that drops - blue/magical, yellow/rare, set, and unique. Magic Find only affects this factor. And only blue/magical quality items increase at a linear rate, while rare/set/unique have diminishing returns (around 300% MF it falls off quite abit for sets and uniques, and in some cases arguably gets worse after >400% MF). Llama has a video that explains alot of this in great detail.
So if an enemy drops Studded Leather for example, having 200% MF means the likelihood of it being a blue/magical quality Studded Leather vs just plain White base is 200% higher than if you had 0% MF. The base odds are best figured out using a drop calculator, I prefer the max roll one.
BigD
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