One of the oldest existing icons — generally dated to the 6th century — is this icon from the Monastery of St. Catherine at Sinai. It is commonly called the Sinai Pantokrator. Pantokrator in Greek means literally “Ruler of All,” but its equivalent in ordinary English is simply “Almighty.”
There are two important things to note about this early icon. First, unlike both the Russian and Greek icon traditions in general, it is not “stylized,” not abstract. So we can see that abstraction for its own sake was not characteristic of all early icons.
The second important thing to note is that if one divides the face down the middle vertically, one is left with two distinct depictions: the Christ on the left of the painting is mild and pleasant:
But Christ on the right side of the painting is severe and angry-looking:
The consensus is that the painter intended precisely that: the two sides of Christ, one the good Savior with his hand raised in blessing; the other the severe Judge, book in hand. If one looks at a large example of the image, it is easy to see that even the manner of applying the strokes of pigment was quite different from side to side.
In an earlier posting I mentioned that the earliest Christians had really no idea at all what Jesus looked like. But gradually, over time, the image as shown here began to take precedence over another type in circulation that depicted Jesus with short, frizzy hair and a sharper chin. But neither image — in fact no image existing then and now — is authentic. They all, like the popular Protestant depictions of Jesus by Warner Sallman, come from the mind of the painter. To put it bluntly, they are imaginary portraits.