I’ve said enough negative things about the Orthodox Study Bible that I need to mention when I find it quite helpful as well. Generally, this is when it is either quoting or referring to various church fathers.
In the note on Hebrew 1:3a, “who being the brightness of His glory and the express image of His person …”
The first half of v. 3 is quoted verbatim in the Liturgy of St. Basil the Great. The brightness of His glory expresses the Son’s nature, His origin from and identity of nature with the Father. He is the Father’s brightness because He is begotten from the Father beyond time and without change. Thus, the Nicene Creed speaks of “Light of Light.” As the sun does not exist without radiating light, so the Father does not exist without the Son (p. 1653, on Hebrews 1:3).
I particularly liked the last sentence. It’s hard to use analogies for the trinity without falling into one or another heresy, but this one does a great deal. The note goes on to state that the “express image” speaks of the Son as distinct from the Father, thus bringing together the two elements of the incarnation—one with the Father and yet with us, truly an icon of God.