1981 saw some major technological milestones: the first manned orbital mission of the Space Shuttle...the debut of IBM's Personal Computer (aka the PC)...the first flight of Boeing's second-gen wide-body, the 767...and the first Delorean DMC-12s began to roll off the line in Ireland. In step with such advancements, Pentax sought to push the technological boundaries of the 35mm SLR, much as they had a decade earlier with their Electro Spotmatic (ES) aperture priority autoexposure model. Only this time it was focus rather than exposure that they were seeking to automate. In late-'81, the ME F would become the first production 35mm auto focus (AF) SLR (with a caveat ;-)) to hit the scene.
Development of auto focus really started to take off during the 1960s, but progress was slow as technology simply was not yet sufficiently advanced to underpin it. Even through the 1970s, when the first prototype AF lenses began to appear at tradeshows, that is just what they remained...prototypes. But with the constant miniaturization of transistors, microprocessors, and photosensitive cells, the stage was being set for a major push during the 1980s. Pentax would prove to be the first to get a production-quality SLR and AF lens to market, but it would come at the cost of being right at the beginning of the development curve and thus a sizeable opening was left for others to improve upon the technology. This is the story of the ME F.
ME F - A Superfly ME super?
The origins of the ME F go back to 1976 and the introduction of the ME by Pentax. The ME was their first compact autoexposure SLR and was the smallest such SLR on the market at the time. The ME was a fairly basic camera: aperture priority-only exposure, 1/1000 sec. top shutter speed, no DOF (depth of field) preview or MLU (mirror lock-up), and no aperture value displayed in the viewfinder. That might seem to make it less desirable, but Pentax was targeting the Canon AE-1 and that's what it took to hit the right balance of features for the price point. They did throw in the best viewfinder in the class (92% coverage at 0.97x with a 50mm lens), and the camera was very responsive with its gallium photodiode (GPD) metering. And all of this in an ultracompact 460 gram (16.1 oz) package :-).
Come 1980, the ME was upgraded to "super" specification:
The ME super would be the starting point for the ME F with the only visible changes being a new set of switches beside the rewind knob/exposure comp. dial and a lensmount with electronic contacts (Called Kf by Pentax. Not to be confused with the later Ka and Kaf electronic mounts). The viewfinder magnification dropped to 0.87x, which would only be noticed if compared side-by-side with the super's. This also had the effect of improving eye relief, which made the ME F a better option for eyeglass wearers. Inside the camera, Pentax added what they termed an EFC (Electronic Focus Control) module. It was based on the concept of using differences in contrast (which came to be known as "contrast-detect AF") to calculate proper focus. This was basically an automation of the manual focus technique of viewing the image on a ground glass focusing screen and manipulating focus back and forth until the sharpest image (or highest contrast) was achieved. While capable of excellent accuracy, this system was slow as it moved the lens incrementally, and then stopped to compare the contrast between two arrays of photo detectors. When the readings from both arrays matched, focus was achieved. EFC would slightly overshoot focus in both directions to confirm maximum contrast. All of this moving...and checking...and moving...and checking...and moving...and checking had the understandable effect of SLOWWWWING down the focusing process and inducing what came to called "hunting" as the EFC would keep moving focus back and forth in its efforts to find maximum contrast. The lower the contrast of the subject, the harder the EFC had to work and it would eventually just keep hunting back and forth, being unable to determine proper focus.
Pentax was fully aware of these limitations and explicitly stated in the manual: "IMPORTANT: When contrast and lighting are insufficient for focusing, the motor will turn back and forth slowly. If this occurs, stop focusing immediately to avoid wasting batteries." And here we begin to detect a whiff of the ME F's downfall. But before we get into that, it is important to note that when used with an ordinary MF lens, the ME F operated exactly as the ME super did (there was still the standard split-image rangefinder/microprism collar focusing aid on a matte screen, with the added option of using EFC to confirm focus (it could also be switched completely off to prevent heavier battery usage if so desired). Pentax managed to shoehorn all of this into the ME chassis with only a 4.5mm (3/16") bump in height and 0.5mm (1/64") more in width. Weight increased less than 10% to 480 grams (16.9 oz). Pretty impressive!
The added switchgear on the left shoulder of the camera is dedicated to the EFC. There is a siding switch with settings of 2.8, 3.5, and OFF. Select 2.8 for use with lenses with maximum apertures of f/1.2 - 2.8. Select 3.5 for lenses with maximum apertures from f/3.5 - 5.6. OFF should be obvious ;-). What happens if the setting happens to be wrong for the lens that is mounted? The EFC will still function, but focus accuracy will be impaired somewhat. This will be less noticeable with wide angles and more noticeable with telephotos. Pentax' choice of green and orange to delineate the 2.8 and 3.5 settings was a bit unfortunate for those that are colorblind, but otherwise worked alright. There is also a second switch below the max. aperture selection slider; this switch activates or deactivates (thankfully ;-)) an audible focus confirmation beeper. And that is as far as the operational differences between the F and the super go.
F for Flop?
For all of Pentax' groundbreaking efforts with the ME F, it was pretty much a failure, saleswise. Production reached over 90,000 units, which doesn't sound terrible on its own, but here is a little context: over the same period, the ME super sold roughly 20 units for every ME F sold. Why? For two basic reasons: 1) The AF of the ME F frankly, sucked. Although theoretically rated as effective down to EV 4, in reality, right in the Instruction Manual, Pentax stated that EFC would struggle with light levels below EV 5.5 (dim indoor lighting, outdoors at dawn/dusk, or in heavy shade or overcast). That, along with the hunting, consigned the ME F's AF to static scenes in good light (and you still better not be in a hurry ;-)). 2) To recoup their development costs, Pentax priced the camera and AF lens at $1,295 USD (all prices inflation-adjusted to 2022) in August 1982. Compare that to an ME super with the 50/1.4 prime at $622 USD and it doesn't take a rocket surgeon to figure out what's going to happen. Those two factors consigned the ME F to a short lifespan (production ended in late-1982 or early-'83) with all USA stock being bought up by Ritz Camera in the fall of 1983 and blown out over the holiday season for $628 USD with the AF lens and $452 USD with the SMC-A 50/1.7 standard MF lens (that was $50 less than an ME super with the same lens :-0).
A large part of the problem was the single AF Zoom 35-70/2.8 lens, which made up over half the cost of the kit when introduced. At 640 grams (22.6 oz) with its 4 AAA batteries and ponderous lower protuberance, it did not handle or balance particularly well with the petite body. The ME II winder improved handling with the AF lens measurably, but that was yet another cost ($155 USD) and still more weight to add (another 440 grams/15.7 oz with batteries) to the package. Optically, the lens was excellent for the era, but the ergonomics and economics easily overcame that advantage. Along with that was the fact that there was never another AF lens option made available. The strength of SLRs is their versatility and ability to use a variety of lenses and other add-on accessories. That was negated in the case of the ME F (and to be fair, every AF SLR introduced before 1985).
The ME F Today
Befitting a model produced in 1/20th the quantity of the ME super, you certainly don't come across ME Fs every day. But that can work in your favor, especially when you find one with a standard 50mm lens. Similar to the situation in late-1983, the ME F can often be had for less than an ME super in comparable condition. Without the collectible AF lens to bump up the price, that makes it a great value for someone who wants a very usable SLR. Switch off the EFC, and it will function identically to the super. If you wear glasses, the longer eye relief of the F will be welcome. I find the EFC to be almost too sensitive in many situations when manual focusing. It takes a very light touch on the focusing ring to keep from overshooting the green hexagonal LED indicator in the viewfinder.
Something to carefully inspect when contemplating a potential ME F purchase is the state of the battery cover. It is a somewhat delicate plastic door with a separate push-button latching system that has often been abused by users who tried to get inside without realizing the need for the release button to be pressed in. Other than that, sturdiness and reliability is on par with the ME super. As on the ME super, the shutter button travel is quite long, which can be off-putting for some. Pentax also advised not to use LR44 alkaline batteries in the camera, only SR44s, as the higher power demands of EFC and the discharge curve of alkalines were not made for each other.
While the ME F didn't succeed commercially as Pentax hoped, it was an influential SLR. It started the production AF 35mm SLR train rolling and pushed the other Japanese manufacturers forward. Within a couple of years, both Olympus and Nikon had also introduced AF models (which also required dedicated AF lenses). It would be Minolta's 7000, introduced in February 1985, that would really put AF SLRs on the map to stay and Pentax would adopt Minolta's basic premise of having the lens focus driven by an in-body motor for their next generation of AF models beginning in 1987.
For commercial success, you need the right product...at the right time...at the right price. The ME F failed on those three counts. It was not mature enough as a design to seriously threaten concurrent MF SLRs in focus performance or ergonomics. It was simply too early in the development curve of AF technology and would quickly be surpassed by competitors. And it was just too expensive to reach the target audience that would appreciate its purported benefits. All that said, it still makes for a great MF camera to use today with a bit of historical cachet thrown in :-).
Pentax ME F User Manual
Inside Autofocus: How the Magic Works, p.77-83 Popular Photography Feb. 1982
Pentax ME super User Manual
Pentax AF Zoom 35-70mm f/2.8 User Manual
Suffers from a quarter-century and counting film and manual focus SLR addiction. Has recently expanded into 1980's AF point and shoots, and (gack!) '90s SLRs. He even mixes in some digital. Definitely a sick man.