An evergreen staple of Sherlockian essay is the "my first encounter with Sherlock Holmes" story.
Those stories often began with receiving a book as a gift from a beloved family member. Did the book have pictures? It doesn't get mentioned too often, but I would guess the larger share of the Canon in print are not illustrated. So that means that, once upon a time, how Sherlock Holmes looked the first time a person encountered him was a mix of Conan Doyle's description and the reader's imagination.
The first chapter of A Study in Scarlet gives us little in the way of physical description: One excited "student" in the lab at Bart's, whose eyes seem to glitter. His has a strong grip. He's a bit theatrical, bowing to an invisible crowd at his accomplishment. In chapter two, Watson gets down to business: "In height he was rather over six feet tall, and so excessively lean that he seemed to be considerably taller. His eyes were sharp and piercing . . . his thin, hawk-like nose . . . His chin, too, had the prominence and squareness which mark the man of determination."
At this late point in the game, those words conjure almost a cartoon Holmes in my mind, as that thin, tall, all-nose-and-chin look has been favored by Holmes cartoonists for a very long time. And was there ever an actor who perfectly embodied them? Not Robert Downey Jr., to be sure. Rathbone had the face, but needed a Jeff Goldblum lankiness. And Benedict Cumberbath, while slim and tall enough, is not encumbered with that stereotypical Holmes nose. (Could he still have been a heart-throb with the big hawk nose? Hmm.)
The point of this digression is that Doyle's words are no longer the starting point for most people's first impression of Sherlock Holmes. And when I say "impression," I mean "the first Sherlock to make a dent." The first Sherlock Holmes who stands apart from the background noise that media deluges us in. Many people's first actual encounter with Sherlock Holmes might have been a car commercial or an add for gummy candy, but no one is going to remember that fleeting glimpse. Your first true encounter with Sherlock Holmes worth mentioning is alway going to be the one that sticks with you.
That Holmes we see in Doyle's original first chapters -- tall, young, energetic, and square-jawed -- could have been either a real looker or a real geek. There was a lot missing from those words that left certain details up to us. Coming to them after a solid diet of Downey, Cumberbatch, or Miller might conjure an entirely different fellow in that lab at St. Bart's than an Ichabod Crane sort, which they might also describe.
How are new media Holmes going to change our first impressions of the great detective? How have they already? One can't exist for centuries without some sort of personal evolution, and now that he's well into century two, first impressions of Sherlock Holmes will definitely be evolving as well.