This computer-enhanced detail is from the oldest known icon of Jesus at the monastery church of Saint Catharine at Mount Sinai. It is usually dated from the sixth century A.D. All later icons of Jesus are clearly based on it, as befits the tradition of iconography.
However, there is a major difference, for all the later ones have the crucifix boldly superimposed on the halo. This may be an indication that this earliest one came from the Syrian Church, in which Jesus was regarded as the Life-Giver, rather than the Saviour.
While this image is copyright, you are given permission to print it out on your computer for your own spiritual use (click on the image below). You might like to experiment with enlarging the image to show only the portrait, without the halo.
"Jesus the Life-Giver"