And the aim of an icon is not to present you with a likeness of the person but with the message, to present you with a face that speaks to you in the same way in which a portrait is different from a snapshot. A snapshot is a very adequate image of the person photographed at a given moment. It’s exactly what at that given moment the person was, but it leaves out very often most of the personality of this particular person, while a good portrait is painted in the course of many sittings that allow the artist to look deeply into the face of a person, to single out features, which are fluid, which change, which move but which, each of them, express something of the personality. And so that the portrait is something much more composite, much more rich and much more adequate to the total personality than a snapshot would be although at no moment was this particular face exactly as the painter has represented it on the portrait. It is not an attempt at having a snapshot in color but of conveying a vision of what a person is.
Now, this being said, we treat icons with reverence, and a number of people in the West think that to us icons are very much what idols were in older times for pagan nations. They aren’t. They are not idols because they do not purport or even attempt at giving an adequate picture of the person concerned. This I have already mentioned abundantly but I will add this. Whether it is in words, in theological statements, in doctrinal statements, in the creeds, in the prayers and the hymns of the Churches, no attempt is ever made in the Orthodox Church at expressing, at giving a cogent, a complete image of what God is. Already in the fourth century St. Gregory of Nazianzen wrote that if we attempted to collect from the Old Testament, from the New Testament, from the experience of the Church, from the personal lives of saints, their sayings and their writings, all the features which reveal to us what and who God is and try to build out of them a completely coherent, complete picture of God, what we would have achieved is not a picture of God; it would be an idol because it would be on our scale, it would be as small as we are, indeed, smaller than we are because it could be contained in our vision, in our understanding.
Source – Metropolitan Anthony Bloom