IF YOU’VE SHOPPED FOR A CAMERA OVER THE PAST TWENTY-FIVE YEARS OR SO, there’s a good chance that you’ve seen a chart similar to the one shown here, which compares the dimensions of variously sized digital camera sensors. Across the history of photography, there have always been a selection of frame shapes and sizes on offer, many passing in and out of existence based on technical advancements or the changing needs of shooters. In the digital era, however, there are more formats existing side-by-side than ever before, each grappling for their chunk of the overall marketplace.
The longest-lasting such configuration is the “full-frame” format, which carries over the basic dimensions of the old 35mm film frame. When introduced in the 1920’s by Oskar Barnack, it sped his development of the Leica and the introduction of hand-held or “miniature” cameras, which freed amateurs from the bulkier “medium format” cameras of the period. With many popular consumer films like Kodachrome created specifically for it, 35mm remained pretty close to a universal format until the 21st century, when early digital cameras began to offer the convenience of ever-smaller sensors. Of these, the APS-C, or “crop” sensor became the new standard of use for DSLRS, compacts and “bridge’ cameras. The crop, as its name implies, delivers a smaller frame area (and fewer pixels) than an FF, changing a larger image’s focal length by a multiplier (or “crop factor”on the chart) of roughly 1.5x. Your lens may say that it’s a 50mm, but, with the multiplier, on your crop sensor camera, your focal length is effectively 75mm.
And so things progress across the chart as you move further to the right on the chart. Each smaller-sized format has its own listed crop factor, with each higher number giving you a smaller percentage of the framing area in a full-frame format. Trends in the camera market have shifted back and forth a lot in the digital age, but none of the listed formats has managed to eclipse the rest to become a truly universal standard. Full-frame is still a factor, but has become increasingly expensive since fewer models are offered than was the case just a few years ago . 4/3rds has its fans, both for convenience and compactness, but, as is generally true of smaller sensors with fewer pixels, it can perform poorly in low light. Cellphone cameras, some of the smallest sensors available, began their run at a definite disadvantage when it came to resolution, with even more image loss once their pictures were translated through apps. However, each new iteration of the technology deals more effectively with these problems, and cels can no longer be dismissed as “not real cameras”. Just depends what you need and what you are willing to pay for/do without/put up with/settle for.
Size discussions off to the side, sensors rise or fall on how efficiently they process light. Some bitty ones do a bang-up job, while some larger ones are flat horrible. Overall they are a miraculous improvement over even great film because their sensitivity and performance can be customized in-camera and on-the-fly. That’s a consistent truth in photography: anything that gets out from between you and the easy making of pictures is a good thing.