Sit still. Karl Johnson needs just 90 seconds. That’s how long it’ll take him to capture, cut, and complete a perfect likeness of your profile. Johnson, 52, is a professional scissor artist and third-generation silhouettist. And he’s coming to Colorado to render your shadow portrait in a quick, $30, five-minute session. His mastery of visual arts sprung with an unlikely source: blindness, in one eye. “I see two-dimensionally, without binocular vision,” he said.