Camera spec sheets bury the numbers that matter under ones that don't. Understanding four fundamentals lets you compare any two cameras and predict how they'll actually perform.
Sensor size & crop factor
The sensor is the digital "film", and its size matters more than any other spec. Full-frame (36×24mm) gathers the most light for the cleanest low-light images and the shallowest depth of field. APS-C is about 1.5× smaller (a "crop factor" that makes lenses look more zoomed-in) and balances quality with cost and size. Micro Four Thirds is smaller still, enabling the tiniest bodies and lenses. Bigger isn't always better — it's a trade-off with price and portability.
Autofocus systems
Modern on-sensor phase-detect AF covers most of the frame and, combined with AI subject recognition, locks onto and tracks eyes, faces, animals and vehicles automatically. This is where recent cameras have improved most, and it's the difference between a sharp candid and a missed one — Sony and Canon lead here. Older or cheaper systems use slower contrast-detect AF that hunts in low light.
Megapixels vs low light
More megapixels means more detail and cropping room, but on the same sensor size each pixel is smaller and can gather less light, so very high counts can add noise in the dark. For most people 24MP is the sweet spot — ample for large prints and heavy cropping. Judge a camera by sensor size and processing, not the megapixel headline.
Video specs decoded
For video, four numbers matter: resolution (4K is standard), frame rate (30p for normal, 60p for smooth motion and slow-mo), whether there's a recording time limit or overheating, and whether 4K is cropped (a tighter field of view) or taken from the full sensor. Uncropped 4K 60p, as on the Canon R10 and R8, is the mark of a strong hybrid stills-and-video camera.