Using a smartphone as a light detector As a blind person, there are often times when I need to be able to detect sources of light. This may be to see if it is light outside, if an electric light has been left on, or if the power LED on an electronic device is on. In the past, Royal National Institute of Blind People (RNIB) sold a device about the size of a marker pen which gave out a sound that changed according to the level of light that it was pointing at. Sadly, RNIB no longer stocks this device, but fortunately it is possible to use a smartphone to do this. Recently, everyone in the building I live in got new door phone systems allowing people to call the flat they require from the outer door and be let in. This door phone system has a privacy setting so you can choose not to hear if someone rings your door. When privacy is switched on, there is a LED that glows to indicate that it is on but there is no other way of knowing whether privacy is on or off. The button that turns privacy on and off is like a doorbell so you can’t tell by the position of the switch. Fortunately, there are a number of apps which turn a smartphone into a light detector. I have used two of them on the iPhone and both these apps are free. Both detected the presence of the privacy LED on my door phone. There is a standalone app called Boop Light Detector. When in this app the phone emits a tone which changes according to how much light there is. It can also vibrate and the vibration gets faster the more light there is. This can be useful if checking for light in noisy environments. You can access the Boop Light Detector in the App Store here. Some time ago I reviewed the Seeing AI app from Microsoft which you can read here. This app has been updated and one of the new features is the light detector channel. This produces a tone which increases in pitch the more light there is. At this time there is no vibration feature but if you are used to using Seeing AI then this could be a good choice. Find the Seeing AI app in the App Store here. Written by Graham Page, Assistive Technology Adviser Want to read more reviews of assistive technology? Visit out Technology page.