The APS-C digital sensor
1999 (Nikon D1); 2000 (Canon EOS D30)
Sensors about 23.5 × 15.6 mm made digital SLRs affordable. Lenses on them see a narrower view than on 35mm film, by a 'crop factor' of about 1.5 (1.6 on Canon).
How it began
Large sensors were very expensive to make, because chips are cut from wafers and bigger chips mean fewer per wafer and more defects. The first affordable professional digital SLRs used sensors about the size of a APS film C frame. Nikon’s D1 (1999) and Canon’s EOS D30 (2000) set the pattern, and the name APS-C stuck.
How it works
An APS-C sensor’s diagonal is about 28mm, versus 43.3mm for 35mm film, so it records only the central part of the image a lens projects. The ratio of the diagonals is the crop factor: about 1.5, so a 50mm lens frames like a 75mm lens on full frame. Depth of field and total light gathered change too. See formats and crop factor.
Why it mattered
APS-C made digital SLRs affordable to amateurs in the 2000s, and smaller lenses designed for the format kept systems light. It remains the most common sensor size in interchangeable-lens cameras.
Limits and what replaced it
With less area it collects less light in total than full frame, so it is noisier at the same exposure and gives less background blur at the same framing. Many professionals moved to full frame as its prices fell.
Today
The most common sensor size in interchangeable-lens cameras, from entry-level bodies to Fujifilm's X series.