The name is historical, not literal.
The first thing to understand is that “1-inch” is a format class, not a ruler measurement. A modern 1-inch-type sensor commonly measures about 13.2 mm × 8.8 mm, with a diagonal of about 15.9 mm. Nothing on that rectangle is actually one inch.
The name comes from older video-camera tube language. In the tube era, formats were described by the approximate outside diameter of the glass pickup tube, not by the size of the active image. A “1-inch” tube class had an active image area of roughly 16 mm diagonal. Digital sensors with a similar image diagonal inherited the same naming convention, so the clearer phrase is 1-inch type, or “one-inch tube-equivalent,” rather than “one inch across.”
Practical translation: for most modern cameras, 1-inch type means approximately 13.2 mm wide, 8.8 mm high, and about 16 mm diagonally. Individual cameras can still crop that area for stabilization, high-frame-rate modes, 4K readout, or aspect-ratio choices.
Why this format belongs beside 16mm and Super 16.
The 1-inch digital format sits unusually close to the world of 16mm motion-picture film. It is larger than the tiny sensors used in many phones, webcams, and older action cameras, but much smaller than Micro Four Thirds, APS-C, Super 35, or full frame. That middle ground is exactly what makes it interesting for video: cameras can stay small, lenses can stay compact, and older C-mount and 16mm/Super 16 lenses often become relevant again.
Standard 16mm film arrived in 1923 when Eastman Kodak introduced 16mm safety film with the Cine-Kodak camera and Kodascope projector. It was intended as a cheaper, safer, more portable alternative to 35mm, but it quickly became more than a home-movie format. Over time 16mm became important for education, documentary, news, industrial films, television, and low-budget production.
Super 16 came later. Rune Ericson’s Super 16 idea widened the image area by using space that standard 16mm workflows had left for soundtrack or perforation-related purposes. Kodak traces the idea to 1966 and the release of Super 16mm in 1969. The result was a wider, more cinema-friendly 16mm frame that could be enlarged, scanned, or finished for widescreen presentation.
Digital descendants and cousins.
In the digital era, the format family split into several branches. Nikon called its 13.2 mm × 8.8 mm interchangeable-lens system CX. Sony’s RX100, RX10, RX0, and ZV-1 lines helped make the 1-inch-type sensor a serious compact-video format. Canon and Panasonic used 1-inch-type sensors in important compact, bridge, and camcorder bodies. DJI, Insta360, GoPro, and industrial-camera makers have pushed the format into drones, action cameras, modular rigs, and specialized video systems. Current 1-inch-type action/cinema cameras should still be checked mode by mode: the published sensor class may be 1-inch type, while stabilization, high-frame-rate modes, or aspect-ratio choices can change the active crop.
There are also near relatives rather than exact 1-inch cameras: the original Blackmagic Pocket Cinema Camera, Blackmagic Micro Cinema Camera, and Digital Bolex D16 are better thought of as digital Super 16 cousins. They are not all the same physical size as a Sony-style 1-inch-type sensor, but they live in the same practical lens-and-field-of-view neighborhood.
Crop factor: use the right number for the question.
Crop factor is not a property of the sensor alone. It is a comparison between one format and another. For still photography, people often compare diagonals: full-frame diagonal divided by smaller-format diagonal. That is useful when comparing total frame geometry across still-photo aspect ratios.
For video, especially 16:9 or wider work, the more useful number is often the horizontal crop factor. It answers the question filmmakers usually care about: how wide does this lens look left-to-right? The simple formula is:
horizontal crop factor = 36 mm ÷ active sensor or film width
That 36 mm reference is the width of a full-frame still sensor. So a 13.2 mm-wide 1-inch-type sensor has a horizontal factor of 36 ÷ 13.2 = 2.73×. The original BMPCC’s 12.48 mm width gives 36 ÷ 12.48 = 2.88×. Both numbers are true, but they answer different questions than diagonal crop.