One must allow the brightness to stabilise. So just keep on watching the breadth until it stabilises well. Once it is established, one can direct one’s mindfulness to the light and will then experience an absorption into that light. It is like putting your head into a bucket of water. That is why it is called absorbed concentration. This is the first jhäna. All this is in the path of serene concentration. Abiding in a jhäna sharpens the minds. Makes it powerful it is like sharpening a knife. It also brings with it great bliss. However, one does not develop insight whilst abiding in a jhäna. The upachära (access) state where the mind is released from the five hindrances in the state in which one practices insight meditation. So if one is able to acquire a jhäna, by all means do so. But do not try to spend all your time in that state. Emerge from it and get on to insight meditation. Otherwise, it would be like sharpening a knife all the time and never using it to cut. Whilst samädhi temporarily tranquilises many defilements, it does not cut or destroy them. It is insight, wisdom, that cuts, destroys and uproot the defilements that bring about dukkha.