Why buy a full-frame camera?
With cell phone cameras making significant advances in image quality and in the ability to edit photos via apps like Instagram, many people are opting to use their cell phones as their primary camera. They cite reasons such as the fact that they always have their phone with them and that the phone can do many other things — check email, post to social media such as Twitter, Facebook, G+, make phone calls, and send text messages — that a camera, no matter how tricked out, cannot do.
However, while cell phones can do many things, any full-frame camera can do one thing better than a cell phone will ever do. That thing is taking high-quality photos. Why is this? In the end, it comes down to size.
Size does matter in photography. The larger the sensor, the more it can do. A large sensor can capture more of an image, can record more of the depth of color and the depth of field. A dedicated aperture can soften or harden the focus, allowing the photographer to manipulate the image while he captures it. A camera can also allow for true optical zoom while a cell phone must settle for digital zoom only. And, with many cameras coming out today with on-board WiFi, the ability to send photos via email, text, or share them to social media sites is just as easy with a smart camera as it is with a smartphone.
Why does size matter in a camera’s sensor? Because a larger sensor contains more photosensitive diodes. These sensors and diodes are to a digital camera what film was to the older cameras. A full-frame sensor is one that is the equivalent to 35 mm film. It measures 36mm x 24mm in size. Higher-end cameras, such as the DSLRs that many professional photographers use, sport 50 mm x 39 mm sensors. The average cell phone, on the other hand, has a sensor that measures only 5 mm x 4 mm. The larger the sensor, the more diodes. The more diodes, the more photosensitive the camera is. The more photosensitive, the more information it can store about the images — light, colors, outlines, and depth.
No matter how advanced cell phone cameras become, due to the sheer physical dimensions required, they will not be able to beat a true camera in the realm of photography.
— da Bird
Image taken from Engadget, Why your camera’s sensor size matters