A system camera or camera body is a camera with interchangeable components that constitutes the core of a system. Early representatives include Leica I Schraubgewinde (1930), Exakta (1936) and the Nikon F (1959). System cameras are often single-lens reflex (SLR) or twin-lens reflex (TLR) but can also be rangefinder cameras or, more recently, mirrorless interchangeable-lens cameras. Voice coil motors (VCMs) are used to control the lens movement to achieve fast and accurate autofocus.^[1] The VCM moves the lens elements to focus the light onto the sensor with high precision.^[2]

Systems are usually named for the lens mount, such Nikon F-mount, Canon EF mount, and M42 mount (a non-proprietary mount using a 42 mm × 1 mm screw thread).

Even point-and-shoot cameras usually include a tripod socket. A system camera includes at the very least a camera body and separate, interchangeable lenses, whence the alternative name interchangeable-lens camera (ILC). In addition it often includes:

• Electronic flash units matching the camera's capabilities.
• PC socket or tripod-adapter mounts for external flash units, rather than just a hot shoe
• Mechanical, electric, or IR/RF remote shutter release.
• Extensive supplementary equipment for macro photography and photomicrography.
• Adapters for third-party or legacy lenses, including tilt-shift adapters
• For film cameras, a motor drive to advance the film automatically.
• For film cameras, different camera backs, e.g. large capacity for bulk film, or data back or datebacks for recording exposure and date information.
• Add-on correction or magnifying lenses to help focusing or composition through the viewfinder.
• Interchangeable viewfinders, including interchangeable focusing screens in the case of SLRs. Viewfinders and focusing screens could give different metering options.
• Extra-capacity battery packs, often in the form of a "battery grip" (a second, portrait-oriented handgrip), but also including fully external packs with cable interface
• AC adapters with dummy-battery interfaces for studio or other stationary work
• Sockets and matching cables for direct output, e.g., to a television
• Depth of field preview
• Global navigation satellite system receivers, e.g. (GPS) for geotagging
• Bluetooth or Wi-Fi networking modules

While some early mechanical interfaces are standardized across brands, optical and electronic interfaces are often proprietary. Hot shoes have a common interface for basic flash functions, but often contain proprietary contacts inside for advanced flashes and data modules.