The Pentax 6×7 (later 67)  is a SLR medium format system film camera for 120 and 220 film, which produces images on the film that are nominally 6x7cm in size (actual image on the film is 56 mm × 70 mm)

The camera is completely battery dependent. Power is provided by a 6 volt PX28 (originally Mercury-specified 1968, and Silver Oxide 1971), but equal substitutes PX28S/4SR44.

The mirror and cloth curtains are mechanically-driven, the timing of the shutter being electrically governed by transistors and a magnet. The combination of resistors routed by the speed setting determine the length of time the magnet remains engaged.

The large cloth curtains as well as the size of the exposure area limits the maximum flash synchronizing speed to 1/30 sec.

The shutter does not fire without film being loaded. However, one can test the shutter by rotating the counter dial away from the empty position while the film door is open and then by closing the film door while still holding the dial, thus facilitating the unlocking of the advance mechanism and operation of the shutter.

It was also possible to check the shutter with a bypass key that was inserted in the frame counter engagement slot and allow for inspection of the shutter while the film door was open.

The frame counter is incremented only while there is film passing over the "main roller" or "counter roller" next to the take-up spool in the camera. The camera disengages the "transport system" when the counter dial (connected to the frame counting control cam) has reached the last frame, or when the counter has returned to the "empty" or start position. The automatic frame counter resets only if the shutter is released before opening the back.

Electromagnetic operation of the shutter means a battery is required to power the timing as well as the holding of the curtain release mechanism when the release button is pressed. When there is a loss of adequate voltage, the camera cannot complete the operation cycle. In this state, the mechanically actuated mirror is allowed to rise, however, the curtain release mechanism would continue past the cycle and not fully disengage the curtains from the primed position. Therefore, the reset procedure will be necessary to bring the mirror back to finish the cycle.

A small button located flush on the right-hand camera front, just below the shutter-release button, is provided for restarting of the mirror/shutter cycle and depressing the shutter release once more will release the cycle. In a situation where the shutter fails to fully operate, the frame is lost.

The shutter release button is standard threaded for pneumatic bulb/cable releases, an accessory timer or the use of a larger accessory ('soft touch') button.

The fingernail-operated latch to the left lower side releases the film door for loading. The film spools are secured by the pins and slot shaped opening at either end of the film spool.

The camera has two twist-lock cams that turn and pull out to open, the left side for the unexposed roll and the right side, known as the "take-up" spool. The differences of the 120 and 220 start length of paper have indicated starting points which are marked above the film plane for lining-up the START mark on the film.

The film advance system is a tension/friction type, the film source side being a tension brake and the take-up side torque/slip clutch.

A counting cam governs the frame count and interacts with the friction system to allow enough slip and movement to accurately space each frame from the beginning of the roll to the end. The counting cam also allows the system to regulate a lock to open and close, allowing the shutter to fire.

This slip system has brought criticism of durability,  as it would slip more over time, causing frame spacing issues as well as disengaging the shutter.

The frame counter system, tied to the counter roller, operates the automatic reset of the counter (i.e. returns it to start) whenever the back is opened, and also sets the regulating of the next frame.