What are megapixels?

When it comes to marketing new handsets, it’s easy to get lost in the sea of jargon surrounding smartphone camera megapixels, picture quality and lens types.

The pixel is one of the most misunderstood aspects of photography, with manufacturers bandying around ever-more outrageous numbers.

But what are pixels, how do they become megapixels, and what’s their impact on picture quality?

Pixel perfect

A pixel is an individual speck of visual data – the smallest unit digital devices can display, and almost invisible to the eye.

Computer monitors tend to display at a resolution of 1920 x 1080 pixels.

That means each of the 1,080 rows of pixels extending from the top of the screen to the bottom contains a total of 1,920 individual pixels.

At this resolution, it’s impossible to see individual pixels – they coalesce to create a single cohesive image with no strobing or distortion.

(To see how sharp they are, try reducing a device’s screen resolution down to its lowest setting, such as 640 x 480).

A one-megapixel camera would typically take a photo at 1280 by 720 pixels – equivalent to 921,600 individual pixels.

Because this figure is close to a million, it allowed smartphone manufacturers of the time to describe their cameras as offering 1MP file quality.

However, it’s important to remember that file quality and image quality aren’t the same thing.

Many camera lenses struggle to capture images in low light, from a distance or while in motion.

In these scenarios, even a high smartphone camera megapixel number won’t guarantee a sharp image.

However, smartphone camera megapixels do give an indication of likely file quality. A 2MP image will be taken at 1920 x 1080 resolution, and should look okay full-screen.

Higher pixel counts make individual images larger, and pack in more detail for sharper and more dynamic-looking shots.

It’s much easier to crop a high-resolution image, zooming in on specific details without ending up with a blocky or low-quality photo.

How does this affect smartphones?

For many years, there’s been an arms race among smartphone manufacturers, trying to tempt consumers by promising increasingly outlandish numbers of pixels.

Some feature 108MP sensors, though these are more beneficial for video recording (including the currently-unnecessary 8K standard) than for stills photography.

In truth, you don’t really need anything more than a 12MP camera, such as the one installed in the front and back of Apple’s latest iPhone 11 Pro.

That’s because a 12MP image will look richly detailed and dynamic on any screen – especially the five-inch and six-inch ones incorporated into modern smartphones.

Indeed, it’s more important nowadays to look for features like wide-angle lenses and longer focal lengths – enabling you to capture more aspects of small or distant environments.

With megapixels long since increased to the point of irrelevance, manufacturers are turning their attention to other niches.

Google’s Pixel 4 offers a five-minute long-exposure astrophotography mode for capturing astronomy images and motion-blurred traffic images (those solid lines of red and white light).

Huawei’s P30 Pro has no less than four rear-facing camera including dedicated telephoto and wide-angle lenses, plus a depth-sensing camera to augment portrait images.

And Samsung’s Galaxy Note 10 Plus incorporates a 12mm ultra-wide camera which is enough to challenge the wide-angle lenses found on professional SLR equipment.

Ultimately, any medium to high-end smartphone will deliver photos packing more megapixels and detail than you’re ever likely to need.