Spy, Mini & Half frame
Some words about these models of cameras.
A half-frame camera is a camera using a film format at half the intended exposure format.
A hidden camera or spy camera is a still or video camera used to record people without their knowledge. The camera is "hidden" because it is either not visible to the subject being filmed, or is disguised as another object. Hidden cameras can be built into commonly used objects such as television sets, smoke detectors, clock radios, motion detectors, ball caps, plants, and mobile phones. Hidden cameras may be used for household surveillance and may also be used commercially or industrially as security cameras. The proliferation and lower costs of video recording devices has led to an increase in the use of hidden cameras for legitimate surveillance need, as well as for entertainment and other purposes.
When still cameras using 35 mm film, originally used for cinematography, were introduced they were widely known as miniature cameras to distinguish them from the then commonplace rollfilm cameras. While the term could be used for a camera larger than a subminiature and smaller than a rollfilm camera, it was mostly used for cameras taking 135 film cassettes, or other 35 mm cassettes.