It has been discovered that the rear camera of the OnePlus 8 Pro smartphone can see through plastic and clothing, using infrared light.

Not an intended feature of the new handset, the ability for the phone to use the infrared to see through materials was made by numerous 8 Pro owners and reviewers this week. The camera app has a number of image filters, including one called Photochrome.

At first the filter seemed somewhat uninteresting, and at the launch of the 8 Pro it wasn't entirely clear what the filter would be used for. You can see some infrared photos here (not of clothing), taken by OnePlus owners experimenting with the Photochrome app before realizing what it is really capable of doing.

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Now, however, 8 Pro owners have discovered that the Photochrome filter uses infrared light, letting it see through certain plastics and fabrics.

Thin black plastic works best, such as that used for television remotes, video game controllers, and the Apple TV set-top box.

YouTube channel Unbox Therapy took things a step further, demonstrating how the camera of the OnePlus 8 Pro can see through some items of clothing.

In the video embedded below, Lewis Hilsenteger showed how the camera can see through his black t-shirt. Holding an iPhone box beneath his shirt, Hilsenteger demonstrated how an image of the iPhone can be seen on the box, through the t-shirt, using the Photochrome filter of the OnePlus 8 Pro.

Infrared technology has been used by smartphones for some time now, and is used by face unlock systems like Face ID on the iPhone. But this is the first time a phone has used it to take photos. Often used by security cameras to enable their night vision feature, infrared light cannot be seen by the human eye, and nor is it visible to regular cameras. However, its radiation, also known as heat radiation, can be picked up by infrared image sensors.

Because infrared light passes through certain materials in a way visible light doesn't, these materials appear transparent when viewed through an infrared camera. In the demonstration embedded below, visible light doesn't pass through the black t-shirt but infrared light does, revealing the iPhone image.

For now, it isn't clear if OnePlus intentionally gave the 8 Pro a feature for seeing through certain materials, or if its use of infrared light was to create interesting photos using the Photochome filter. The images produced by the filter are of quite low resolution, and it is generally quite difficult to see any detail through plastic and fabric.

Further examples are embedded below, showing how products with thin plastic cases like the Apple TV and a security camera, appear partially transparent when viewed through the phone's infrared-powered Photochrome filter.

However, given the phone can see through some clothing, there are obvious privacy issues to be addressed. It seems likely that OnePlus will issue a software update to turn down the phone's infrared abilities, or remove the Photochome filter entirely.

This is reminiscent of an incident in 1998 where Sony was forced to recall a camcorder that had an infrared feature to enable night vision, but which could inadvertently see through clothing.