If you want to grab a quick snap of whatever happens to be on your smartphone screen you could find another camera and take a picture of your phone’s screen. Or, if you want to look less like a luddite, you could take a screenshot.
As an open source operating system different companies will make tweaks to it so it may differ between devices. However, stock Android (the original version released from Google) that you’ll find on a majority of handsets including Google’s own devices works lets you take screenshots like this:
If you’re using version 4.0 or higher (Ice Cream Sandwich) then you just need to hold down the volume down and power buttons on your handset to grab a screenshot.
All Windows Phone users running version 8 have the ability to take a screenshot built into their devices. Hold down the ‘Home’ and ‘Power’ buttons simultaneously.
All version of Apple iOS have the ability to capture screenshots. Simply press and hold the menu button, then press the power/lock button to capture an image of whatever is on screen.