Do I really need... A dual camera?

What does it do?

An increasing number of smartphones come with two cameras on the back. These can be used separately to take different kinds of pictures, or combined to mimic depth-of-field effects.

Why would I want it?

Full-size cameras can use different lenses, or adjustable ‘zoom’ lenses, to vary focal length, bringing action closer (telephoto) or fitting more in (wide-angle). They let you adjust the aperture, or ‘f-stop’, to let more or less light in. A low f-stop with a big image sensor creates a shallow depth of field, so the object in a photo can be sharp while the background’s blurred, an effect known as ‘bokeh’ (pictured). Phone cameras have a small sensor and fixed focal length, so your options are limited. Dual cameras combine simultaneous shots to simulate bokeh. In some cases they have different focal lengths, giving you a choice.

What’s the catch?

One camera, as in Huawei’s phones, may take only black-and-white pictures (the iphone 7 Plus’ dual cameras – pictured – are both colour). Simulated depth of field, or ‘fauxkeh’, sometimes works but can create odd splotches. Not all dual cameras have two focal lengths.

So can I do without it?

Yes, but it’s interesting to see phone cameras doing more of what ‘proper’ cameras can, reducing the need to carry both. Although the laws of physics tell us a smartphone camera will never match a full-size DSLR, digital trickery can help it get surprisingly close in some respects.