I like the way Mark's description translates to my mind's eye. It is much different than I had pictured, which was more of a white, glowing process. Also, it is fascinating to see connect the overshadowing cloud with events from the Old Testament.
... Mark tells us that the garments of Jesus became radiant. The word he uses (stilbein) is the word used for the glistening gleam of burnished brass or gold or of polished steel or of the golden glare of the sunlight. When the incident came to an end a cloud overshadowed them.
In Jewish thought the presence of God is regularly connected with the cloud. It was in the cloud that Moses met God. It was in the cloud that God came to the Tabernacle. It was the cloud which filled the Temple when it was dedicated after Solomon had built it. And it was the dream of the Jews that when the Messiah came the cloud of God's presence would return to the Temple. (Exodus 16:10, 19:9, 1 Kings 8:10, 2 Maccabees 2:8.) The descent of the cloud is a way of saying that the Messiah had come, and any Jew would understand it like that.
The Gospel of Mark
(The Daily Bible Series, rev. ed.)