Red screen test
Check if your red screen filter is actually doing its job. If the blue block below looks black to you, you're good. If you can still see blue, your filter isn't really filtering.
Click anywhere on the screen to exit fullscreen mode
How to test your red screen filter
- Enable your red screen filter (Lumiv, f.lux, Iris, or any blue light blocking software)
- Look at the blue block above or click "Show Full Screen Blue"
- If it looks black or very dark, your filter is working
- If you still see blue, the filter is letting blue light through
Why use a red screen filter?
Red screen filters block all the blue light coming out of your display, which is the part that messes with your melatonin and keeps you up at night. Night Shift only dims blue light a bit. A true red screen cuts it out entirely.
What is a red screen?
A red screen only shows red wavelengths — no blue, no green. That matters at night because red light doesn't suppress melatonin the way blue does. We've been staring at firelight for a lot longer than we've been staring at LEDs, and our bodies haven't caught up.
Don't want to think about it?
Lumiv handles this on your Mac automatically — it knows when the sun sets where you are and shifts your screen so you don't have to remember to flip a switch.
Download Lumiv for Mac