If you want a flattering profile picture - don't use a selfie

On social media of all kinds, the selfie is by far and away the most common form profile picture.  Before we leave anyone behind, by "selfie" we mean self portrait.

Selfies are normally taken with a smartphone facing backwards and held at arms length.  Those seeking a full length shot will often resort to a mirror, although this makes the "selfieness" of the shot far more apparent.

The selfie certainly has its merits.  It's quick, easy, you can take one almost anywhere and crucially you don't need help.

However, for those wishing to show themselves off to their best advantage, whether on Facebook, Twitter or an online dating site, the selfie is definitely not to be recommended.

To explain why, we must get a little bit technical - I will try to be succinct.

The focal length of a lens will lend certain qualities to an image.  Wide-angle lenses tend to stretch everything out, whereas telephoto lenses compress a scene. Two easy examples:

We've all been to look around a house or flat, only to find that the rooms are much smaller than they looked in the estate agent's materials - this is a wide angle lens in action.

You may also have seen pictures or television footage, of airliners packed impossibly close together on the approach to somewhere like Heathrow.   This is a telephoto lens in action - the aircraft are miles apart.

On cameras which used 35mm film, a lens with a focal length of 50mm was considered "normal".  Normal in that it neither made objects appear closer or further away.  Normal in that 50mm doesn't really compress or stretch an image.

50mm could be and is used for portraits, but it's not really until you reach a focal length of 85mm, 105mm or even 135mm that you start to get really flattering results.

By contrast, if you wanted to take a comedy picture of a horse showing you its teeth, where it looks like the beast has a massive nose and is literally about to jump out of the page, then you might go for a really wide angle lens like an 18mm.

Now we come to our smartphones.  Obviously they vary between manufacturers but as a guide, the iPhone 5 has a focal length of 4.1mm.  In old money this is phenomenally wide.

However, due to what is known as "crop factor", which you can read about elsewhere, the field of view is equivalent to a 33mm lens on a film camera.  Optically though, it is still a very wide-angle lens.

Now 33mm (or its equivalent) is a great semi wide angle, walkabout, touristy, snap everything, do a few group shots, field of view to have.  So long as the camera isn't too close to the subjects, distortion from that wide lens will be minimised.

Because the field of view is quite wide though, filling the frame with your handsome/pretty face requires the camera to be quite close in.  Less than arms length certainly, and probably somewhere between 18-24 inches.

So now we have the worst possible portrait scenario.  An exceedingly wide-angle lens, coupled with a very short distance between camera and subject.  Expect the following - huge nose, long face and ears vanishing around the back of the head.

That's before we consider that you can't look natural while holding an arm out in front of you, or the whole host of other things that go into making a beautiful portrait.

So, no using selfies as profile pics.  Unless you want to look like a comedy horse.