Camera sensor size explained: why it beats megapixels

Bigger sensor, more light

A larger sensor has more surface area exposed to light, so it collects more light, and a stronger signal holds up better when the room gets dark. That's the core reason a full-frame camera pulls a cleaner image out of a dim room than a smaller sensor with the same megapixel count. Its pixels are bigger, so each one gathers more light.

The same physics gives big sensors their shallow depth of field, the narrow band of sharp focus behind that creamy background blur. Portrait shooters prize the look. It also narrows the in-focus range, though, which can make autofocus harder to nail.

In-body stabilisation

In-body image stabilisation (IBIS) shifts the sensor itself to counter hand shake, and it works with any lens you mount. It typically buys somewhere between two and four stops of hand-holding, and some camera-and-lens combinations claim up to around eight. The result is sharper handheld shots in low light and smoother handheld video. If you shoot without a tripod, few features are worth more.

Autofocus: phase vs contrast

Modern cameras rely on two focusing methods. Contrast-detection is accurate but slow. Phase-detection is much faster and can lock on in a fraction of a second. So today's cameras combine both in hybrid systems, then add subject recognition that tracks eyes and faces across the frame. Photograph anything that moves (kids, pets, sport) and a proven phase-detection hybrid AF system matters more than almost any other spec.