Pentax's early autofocus SLR — the ME-F, aperture-priority, K mount, 1981.
The Pentax ME-F is a 35mm film SLR introduced in 1981, built on the compact M-series body and notable as one of the earliest production SLRs to offer in-body autofocus assistance. It extended the aperture-priority ME line with a focus-detection system that worked with a dedicated power-zoom AF lens, while remaining fully usable as a manual-focus camera with ordinary K-mount optics. It was sold under the Pentax name in the UK and Europe.
It is a 35mm single-lens-reflex camera using the Pentax K bayonet, with aperture-priority automatic exposure carried over from the ME Super. Metering is through-the-lens, and the electronically-timed focal-plane shutter is selected automatically when the aperture is set on the lens. The distinguishing feature is an electronic focus-detection module: with the special AF lens it could confirm or drive focus, and with standard lenses it provided a focus-confirmation aid in the finder. The body relies on batteries for metering, exposure timing and the focus electronics.
The ME-F appeals to collectors and users interested in an early step toward autofocus, and it works well as a compact aperture-priority manual-focus SLR for travel and general use. The autofocus function was slow by later standards and tied to a scarce dedicated lens, so most owners use it with conventional K-mount glass and treat the focus aid as a bonus rather than the main draw.
When buying used, inspect the perishable foam light seals and mirror-damper foam typical of M-series bodies. Verify the meter responds to light and the aperture-priority automation produces sensible speeds, remembering the shutter is battery-dependent and needs good cells to fire accurately. Test the focus-confirmation electronics and finder lamps, check the shutter for even exposure and no capping, and feel the film advance and rewind for smoothness. Look for prism haze or desilvering, and note the original AF lens is hard to find.