Title of 70s sci-fi / horror / fantasy movie about tattoos?!

I remember seeing this movie as a kid!. It was about 2 guys by a campfire!. One guy had all these tattoos on him!. And when the other guy looked at a particular tattoo, he'd have a cut-away vision that somehow related to the tattoo he was looking at!. Eventually these visions drove him insane and he tried to kill the guy who had the tattoos!.
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