This question came up in the Online 10-day Retreat Nov 3, 2020, guided by Delson Armstrong. Day 3 was part of a daily 30 -minute discussion on the suttas, the Dhamma talk and reflections.
Slightly edited to improve readability
What I’m referring to is the brightness of mind, as opposed to the dullness of mind. Meaning, a mind that is well collected, well unified, and is constantly aware, constantly attentive, without distraction. It is constantly collected around that quiet mind, that awareness.
But the light objects, the signs of Formations or images that arise, are not part of that bright mind. They just arise as part of subtle Formations, that are rooted through our processes of Kamma, and things like that, that will just come about and will arise.
But that is different from what is the bright mind. The bright mind is generally a mind which is fully attentive, fully conscious, and unwavering. It has a steady presence of mind.
Watch it here