The six sure signs that a photograph has been retouched

One of the perils of picture editing in the digital age is finding yourself duped by a fake image or a photo that has been manipulated. Guardian picture editors scan up to 30,000 images a day – often selecting at pace those that seem worthy of publication – especially when feeding the hungry beast that is the Guardian website.

But, as a University of Warwick study has discovered, spotting a fake is a tricky task, made almost impossible by the sophistication of artistic tools now available to a skilled photo manipulator.

Researchers found that four in 10 people couldn’t tell a digitally manipulated picture from an untouched one. An individual can seamlessly become a crowd, a clear sky can be replaced by a tempest, textured skin made smooth, waists pinched in. There is almost no limit when it comes to creating a scene that – even to the most astute beholder – is apparently genuine.

So, how can you tell a manipulated photo from a genuine image? Here’s how we might spot a hoax while sifting through the daily deluge.

Verification

It’s always worth interrogating an unlikely situation by verifying it through alternative sources. For example, are there similar pictures in the series? Were other witnesses able to corroborate the evidence?

Light and shade

Shadows or highlights that don’t correspond to the direction of light – or that aren’t there at all – should always raise suspicions.

Patterns

This can often be the simplest to spot, as our brains are very attuned to noticing patterns. Any repetition of pixels can be an indicator that parts of the image have been cloned.

Reflections

Another dead giveaway for a careless manipulator. Watch out for, say, a deep, moody sky that isn’t reflected as it should be in water.

Quality

Differences in quality or varied pixelation across a single picture, or sequence of images by the same photographer, can set alarm bells ringing.

Size matters

Perspective can play a part, too. Take the sensational story of the giant rat found in Hackney, east London, last year. Thanks to a perspective trick, the animal appeared to be about 1.2 metres (4ft) long – when in fact it was more likely to be half that size.