Pentax ME F

For photographers younger than about 40, it’s probably hard to imagine a time when autofocus cameras didn’t exist. Pentax brought the first one to market in 1981, as the Pentax ME F. They designed an autofocus lens, and modified the chassis of their compact M-series (ME and ME Super) cameras to take it. The focusing motor was built into the lens, and it was dog slow. But it worked, and it showed that autofocus was no longer a pipe dream.

Pentax ME F

Check out that huge honking lens! It’s a 35-70mm f/2.8-22 zoom lens of seven elements in seven groups. It’s a “pumper zoom” — pull it in to zoom in, push it out to zoom out. It needs its own batteries, four AAs, with which this lens weighs a shocking pound and a half. Just the lens! It makes the ME F hopelessly front heavy, negating the small, light body’s advantages. It is so large that when you attach it to the camera, the bottom plate can’t rest squarely on a surface.

Pentax ME F

Here’s a closer look at the lens. An on/off switch is at the bottom front of the lens; strangely, an indicator is green when the lens is off and red when it’s on. Notice the button on the top; there’s one just like it on the side you can’t see in the photo. You press and hold one of those to focus the lens. Even though the focusing motors are in the lens, the focus confirmation system, which tells the lens when it’s locked focus, is inside the ME F. Therefore, this lens autofocuses only on an ME F body.

35-70mm f/2.8 SMC Pentax-AF

You can mount any other K-mount lens as well, but you must focus them manually. Fortunately, the ME F’s focus confirmation system works with any lens. When you achieve focus, it lets you know with a green LED in the viewfinder.

Pentax ME F

The ME F is uses a vertical-travel, metal focal plane shutter that operates from 4 to 1/2000 second. It syncs to flash at 1/125 second. Like the ME Super, it offers both aperture-priority autoexposure and a push-button manual mode. To use manual mode, turn the top dial to M, use the aperture dial on the lens to set aperture, and use the two buttons next to the dial to move the shutter speed up and down.

Pentax ME F

You could get the ME F in satin chrome over black, or in all black. I’ve never seen an all-black ME F except in a photograph.

This ME F was an incredibly generous gift to the Jim Grey Home for Wayward Cameras. Check eBay for working bodies with the zoom lens included and you’ll see why I wrote incredibly before generous. These are highly collectible and prices reflect it.

Another camera I reviewed with a focus-confirmation system is the Canon AL-1 (here). Also check out my reviews of the Pentax ME (here) and ME Super (here), on which the ME F is based. Or read my reviews of these other Pentax SLRs: the KM (here), the Spotmatic F (here), and the ES II (here). Or check out all of my camera reviews here.

To turn on the ME F, you not only have to turn the main dial to Auto (or M if you want to use manual mode), but you also have to turn on the lens (on the bottom at the front), and focus confirmation using the switch left of the prism. If you want to hear the focus confirmation beep, you need to turn on that switch too, below the focus confirmation switch. Don’t forget to turn them all off when you’re done!

I put a roll of Agfa Vista 200 through this ME F when I got it, and I found the meter’s readings consistently led to heavy underexposure. Thank heavens for Agfa Vista’s wide exposure latitude. Here’s a photo from that roll; it’s typical.

In Stonegate

I was surprised by this misbehavior, as this ME F had been cleaned, lubed, and adjusted just before I got it. The meter should have been spot on. This ME F’s underexposure is a mixed bag; sometimes it was way off as above, and other times it wasn’t so bad, as below.


I decided I’d send it to Eric Hendrickson, the premier Pentax repair person, to have the meter calibrated. Before packing it up I decided I’d remove the batteries. The fellow who gave me this ME F told me to read the manual first, because it has some usage quirks. I failed to do that. Naturally, the first quirk involves opening the battery door. It includes an imprint of an arrow and the word OPEN, suggesting you slide the door sideways to pop it open. You do, but only after you press in the black button next to that door to release the door. Idiotically, I tried to force that door open. To my shame, that broke off the tabs it that hold it closed.

I bought a parts ME F body off eBay for its battery door. When it arrived, I noticed that the sticker on the door showed pushing the button in and then sliding the door open. How did I not notice that on the other door? So I looked at it, and saw that its instructions sticker was different: half the text s in Japanese, which I don’t read; the other half is so tiny that even with my reading glasses, I have to squint to see it. But it did tell me exactly what to do. Facepalm. Will I ever get over my deep-seated feeling that to read the instructions is to admit defeat?

Pentax ME F

In replacing the battery door, which involved removing the bottom plate, I lost a tiny spring under the door-release button. I barely touched it and it sprang away, gone in an instant! Without that spring, the button doesn’t work. But I had that spare body, so no worries, right? I got the spring from that body and set it in place — and then accidentally nicked it with my needle-nose pliers and made it vanish, too. I searched my work area for a long time but found neither spring.

After clenching my jaw and muttering a long string of four-letter words, I bought another parts body off eBay — and then lost my nerve for three years. This March I finally screwed together my courage and tried again, this time with success. I finally had an ME F that could hold its batteries! Those batteries, by the way, are four 1.5-volt 357, LR44, or SR44 cells.

Then I reached out to Eric Hendrickson to see if he had time to calibrate my camera’s meter, and he replied that he no longer works on ME Fs. Drat and double drat!

I shot the camera without film inside at EI 400 to find out exactly how the meter was misbehaving. I discovered that most of the time it underexposed by about a stop, but randomly it would read six or seven stops of underexposure. When I switched to EI 200, the camera overexposed by about a stop. I discovered that EI 320 read close to right for ISO 400 film most of the time. So I loaded some Ultrafine Extreme 400 and took the ME F for a long walk.

No outlet

This is the slowest autofocus I’ve ever experienced. I am neither surprised nor disappointed — this is very early autofocus, after all, barely more than a prototype. It had to be clear to Pentax even before they released this camera that this system was not commercially viable. But it worked, and that’s what mattered. The industry could innovate from there to perfect the idea.

Focus under the tree

The ME F focuses at the center of the frame. When you press one of the focus buttons, the lens begins what I’ve come to call The Process: a series of focusing increments until it achieves focus. Snerk, snerk, snerk — the lens turns a little, checks for focus, turns, checks, turns, checks, until it locks onto the subject.

Retention pond

The lens has no way of knowing whether the subject is in front of or behind the starting focus point. It has to just keep doing The Process until the focus confirmation system in the camera body signals that it’s locked on a subject. The lens can change direction only at infinity and at minimum focus distance. Whichever direction it was last going, when you press the focus button, that’s the direction it goes in. If the lens’s current focus direction is outward, but the subject is inside the starting focus point, the lens has to go all the way out to infinity, then reverse and come back to find the subject.


As you might guess, this autofocus system is not nearly fast enough for moving subjects. Also, it needs pretty strong contrast to be able to see what you want to focus on. It can’t focus on a flat wall, for example. Move the center of the frame to something on the same plane that has that contrast, focus, and then recompose.

A random curbside stove

You can focus this lens manually, too, but there’s no fat, rubberized focusing ring as on a normal Pentax-M lens. You have to twist the bare metal of the narrow outer ring. Twisting it fights the autofocus motors, which whine in protest. But as far as I know it doesn’t damage those motors.

On a couple frames, I focused manually and used focus confirmation to see how it went. The beeper quickly proved to be annoying so I turned it off. The LEDs in the viewfinder worked fine, though. They are a red >, a green o, and a red <. When the green o lights, you’ve achieved focus. The split image patch in the viewfinder worked even better, though.


This 35-70mm zoom is a surprising performer, offering good sharpness even at f/2.8 and no distortion that I could detect, even at the wide end. It’s a shame Pentax never made this lens in a non-AF version.

At the end of the roll, the film wouldn’t rewind. The rewind knob turned freely, with none of the familiar resistance of dragging film back into a canister. I removed the film in my dark bag and spooled it into a black film canister until I could develop it. The canister itself wasn’t faulty so it had to be the camera. But good heavens, how could this possibly be broken? I still had one of my parts bodies out, so I compared them. The prong on my good ME F body is too short! How is this even possible?

“Good” ME F
Parts ME F

Now I wonder if this camera was ever used before I received it. Fortunately, it’s easy to get that prong out: hold it fast (such as by wedging in a thin screwdriver) and turn the rewind crank, and it unscrews. I swapped this prong in these two bodies.

To see more from this camera, check out my Pentax ME F gallery.

The Pentax ME F is a historic camera, but its balky and slow autofocus make it not a useful system today. That’s not to say you should turn down a working ME F body if you find one — just attach a manual-focus lens and go to town. It’ll work like an ME Super, a delightful compact camera in its own right.

If I ever find someone who can calibrate its meter, I’ll update this review.

If you like old film cameras, check out all of my reviews here!
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14 thoughts on “Pentax ME F

  1. Very interesting review Jim. I never tried one of those early autofocus cameras, I remember at the time they looked so advanced, in reality they are just ugly and apparently useable only if you have plenty of patience!

  2. Arhphotographic says:

    Thank you for your detailed article really interesting. Thank you also for reminding me why I should be content with my me super, which as you commented is all the camera you need. I was looking the Canon T80 which also comes with a ridiculous bulbous lens , but maybe not.

  3. Subject camera came from the personal collection of a retired Pentax employee. I bought it because it is very rare to find a complete ME-F kit. I have acquired a number of camera bodies and lenses from this gentleman over the years and many of them appear unused. I need to ask him about the mystery of the short rewind prong. I never put film through the camera before passing it on to you.

    • It was remarkable to me how many parts ME F bodies were for sale when I was buying them on eBay. And I was surprised how quickly my two parts bodies sold when I listed them! Yet when you search eBay, complete ME F kits are not common at all. I thank you again for your generous gift!

    • I’ve never had such a repair adventure with an old camera before! I still feel embarrassed that I caused most of this camera’s problems.

  4. P says:

    Nice review of an interesting piece of camera history. Sorry you had so much trouble with it. By the way, when working with tiny metal parts from a camera or anything else, the best (and super cheap) investment you’ll ever make is a good quality magnet. That way, when a part inevitably “springs” away from you, you can quickly run your magnet around the workspace and floor to reacquire it right quick. It probably works nine out of ten times in my experience. Just make sure you’re not waving it around any magnetic media, such as old audio or video tapes, or mechanical HDD’s. If you still have CRT’s around, keep it away from them too.

    • Good idea on the magnet. Perhaps it could have found the spring. But that spring is super springy — it might have traveled a long way. But a magnet would definitely find the screws I drop.

  5. matt says:

    Autofocus is nice, but once I got the hang of the split prism, I wished I had one on my digital camera too… it would really help with I can’t use the autofocus, for whatever reason.

  6. Wow, what a ride with that camera. It all sounds something I would do. I bought a magnet on an extension to find things I lose in my carpet. It has save me a few times in terms of pinging springs and rolling screws.

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