Why a phone camera will never be as good as a DSLR

samantha smith
By Samantha Smith

camera©iStock.com/Roman_Gorielov

IT'S DIFFICULT to remember a time when we weren't all wandering around with really quite powerful cameras in our pockets, but for most of us it was only around five years ago.

That's because in 2010 Apple released the iPhone 4 - and almost overnight a new benchmark in image quality was set. The 5MP main camera took photos that were properly exposed, and brighter and sharper than anything we'd seen before.

Since then we've seen megapixel counts rise, low light performance improve, and a general rapid improvement in specs and decrease in price that means even budget smartphones have pretty decent cameras on board.

But we have to remember that mobile phone cameras punch way above their weight considering their size - and in the end, size is the factor that's always going to prevent the camera in a smartphone from being as good as a basic DSLR with a good lens.

Sensor size

The reason that DSLR cameras can take images full of so much detail, even when the picture is greatly enlarged, is that they contain large sensors. The bigger the sensor, the more light and information it can capture.

Consider that the best smartphone cameras contain sensors of between 1/2.3 and 1/3 inches (a maximum size of 6.2 x 4.6 millimetres), while even budget DSLRs will use an APS-C sensor (at least 22.2 x 14.8 mm): the surface area of the sensor in an average DSLR is at least 12 times greater than that in the best smartphones.

Now consider that the bigger the sensor, the bigger the individual pixels on that sensor can be, even when we crank up the megapixel count - which is why a higher megapixel count doesn't always mean better photos.

Why not make the sensor bigger?

So can't the smartphone manufacturers just increase the size of the sensor? Theoretically, yes, but in practice that causes problems. One of the biggest issues is heat: the larger the sensor, the hotter the handset will get.

Firstly the sensor itself, like every other component in the phone, will get warm when in use - especially when we're shooting video rather than simply taking a quick snap.

But perhaps more importantly, large sensors reduce the amount of space available for the heat generated by the rest of the phone's components to be dispersed - which is crucial when the phone is charging or we're doing something intensive like gaming.

Making the handset bigger or thicker helps with heat management - and while in the past manufacturers have shied away from making bigger handsets, the popularity of the iPhone 7 Plus and other larger phones like the LG G5 could help pave the way for bigger sensors - but they're highly unlikely to ever match those found in a DSLR.

The biggest sensors

In the meantime, the biggest sensor available in the current crop of smartphones is 1/2.3 inches - found in the LG G5, HTC 10, Google Pixel, and all of the Sony Xperia X series.

Samsung's Galaxy S7 handsets feature slightly smaller 1/2.5 inch sensors - and continuing their tradition of getting more out of less, Apple's smartphone cameras have had 1/3 inch sensors since the iPhone 5S.

Optics

The more obvious difference between a DLSR and a smartphone camera is the choice of optics.

DSLR lenses are sold separately from the camera bodies, with different lenses designed for different purposes. Despite some notable efforts with zoom lenses and the like, smartphones generally favour very simple optics, with no (or very little) room for manoeuvre.

It's this lack of manoeuvrability that really limits them, in a variety of ways.

FOCAL LENGTH: The distance in millimetres between the optical centre of the lens and the surface of the sensor when the camera is focused on an infinite point. Expressed in terms of the equivalent focal length for a 35mm lens.

Because we tend to like our smartphones thin, the focal length tends to be very short - usually between 20mm and 30mm, sometimes up to 40mm. The shorter the quoted focal length, the wider the field of view, which is why many selfie cameras are touted as having wide angle lenses.

More obviously, the fixed focal length means there's no optical zoom. Any zooming in we do will be of the digital variety - which is basically taking a picture at normal size and resolution, but then cropping and enlarging just one area.

A smartphone with a higher megapixel count should manage this better than one with fewer megapixels, but again it depends on how much information those pixels can deal with in the first place.

It is possible to buy lens accessories to give us more options, from optical zooms to macro and fish-eye attachments.

Image stabilisation

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Even the best DSLRs will take blurry pictures if we can't hold them steady enough, or if we need to take a longer exposure without some sort of support or tripod.

Because of their size and weight, the makers of most DSLR cameras assume that if we want to take longer exposure photographs, we're either going to find something to rest on, or invest in a tripod or monopod.

But they also recognise that image stabilisation (IS) is quite desirable (if not always useful) so most offer some kind of optical image stabilisation in at least some of their kit.

Whether it's built into the camera body or the lenses, there's plenty of room - relatively speaking - for the gyroscopes and gimbals that work together to keep the lens or sensor stable.

Image stabilisation is far more useful and desirable in small cameras and mobile phones, because their small size makes them ideal for catching impromptu moments in a wide variety of lighting conditions.

Obviously it's going to be expensive to scale down the kind of image stabilisation available in a full sized camera to fit inside a mobile phone - so where we do find IS in handsets, it tends to be of the electronic variety, which relies on processing to remove blur after the image has been taken.

But that's not to say that OIS isn't an option - although it still tends to be reserved for the newest flagship models: the Samsung Galaxy S6 onwards, the LG G5 and V20, the HTC 10 (which uses OIS on both main and selfie cameras), and the iPhone 7 and 7 Plus.

Where smartphones win

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We've already touched on the main advantage smartphone cameras have over DSLRs: convenience. Very few people are willing to lug a DSLR around with them just in case they spot something they want to snap, but most of us have our phones with us most of the time.

Smartphones are also set up for sharing the results instantly, and there are plenty of apps, filters and quick image processing tolls available to make the best of any less than perfect shots we take.

These two factors alone are why smartphones have made a serious dent in the sale and use of point and shoot cameras - even though the latter still just about have the edge in terms of image quality, for the same reasons as their bigger, more serious, cousins.

So while mobile phone cameras do lag behind DSLRs it's not by as much as we might expect, and it would be almost foolish to expect them to catch up - but for those of us who want to get the best image quality possible from our smartphone cameras, there are options.