Eli5: Why does purple light come from a remote when seen through a camera

Question

Why?

In: 1

Answer 1

The remote uses infrared light to send a signal.

The camera sensors can detect infrared light but they cannot distinguish it from other colours, so it appears as purple light on the image.

It’s actually very useful in some circumstances, and many professional cameras have an IR filter to stop it showing up and ruining your images. But astronomical photography sometimes uses IR so they are basically just normal DSLRs sold without that filter on them.

Even the Raspberry Pi camera has both options, with or without filter. Because the way the sensors are made, they automatically pick up IR light too, but most people will want to use a filter on them to make the image more “natural” to the human eye (i.e. only seeing what the human eye would see)

It’s actually a good way to test if a remote is working, point your camera at it and see if it’s still blinking when you press a button.

Answer 2

The remote uses infrared light to send a signal.

The camera sensors can detect infrared light but they cannot distinguish it from other colours, so it appears as purple light on the image.

It’s actually very useful in some circumstances, and many professional cameras have an IR filter to stop it showing up and ruining your images. But astronomical photography sometimes uses IR so they are basically just normal DSLRs sold without that filter on them.

Even the Raspberry Pi camera has both options, with or without filter. Because the way the sensors are made, they automatically pick up IR light too, but most people will want to use a filter on them to make the image more “natural” to the human eye (i.e. only seeing what the human eye would see)

It’s actually a good way to test if a remote is working, point your camera at it and see if it’s still blinking when you press a button.