Red Screen

What can you use a red screen for?

• Stargazing and star charts: Turn on night vision mode and use the dim red light to read a paper star chart or find your gear. It's much gentler than white light.
• A little light at night: Getting up in the middle of the night and only need a little light? Pick dim red and turn the brightness down so you don't light up the whole room.
• Checking red subpixels: On a red screen only the red subpixels light up, so a dark one is easier to spot. For a full check, use the dead pixel test.
• Red light or backdrop for photos and video: Use a tablet or a second monitor as a small red light or a backdrop. Pick pure red for something vivid, or orange red for a warmer look.

Why stargazers use dim red light

When you step outside from a bright room, your eyes need time before you can see faint stars. This is called dark adaptation. Stargazers use dim red light to read charts and handle gear because it's less likely to undo that adjustment. One flash of white light and you may have to wait all over again.

The dimmer, the better. Turn your phone or tablet brightness all the way down first, then pick dim red and lower the brightness here. Night vision mode sets dim red and 20% brightness in one step, and the full screen controls turn dark red too.

If you're observing with other people, keep the screen pointed toward yourself, not at them.

What is a subpixel?

Every pixel on a screen is made of three smaller subpixels: red, green, and blue. When all three are fully on, you see white. On a red screen only the red subpixels are on, and green and blue are off. Look closely with a magnifier or your phone's macro camera and you'll see a grid of red cells.

If one cell stays dark, or you see a green or blue dot on the red, it may be a dead or stuck subpixel. Subpixel layouts vary between screens; the diagram below shows the common vertical stripe layout. Check red, green, and blue separately. The full process is in the dead pixel test.