Andrew Huberman· PhD
What you're looking for is a red light unit that provides red light and maybe far-- near infrared-- excuse me-- light as well. So something in the 650 to 720 ish nanometer range. And you'll want to view that at a distance of about a foot and a half to 2 feet. And you don't want it to be so bright that it's painful to look at because you don't want to damage your eyes.