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Pentax M - The Compact SLR Series

With a resurgence of interest in film photography along with the ease which vintage K Mount lenses can be used natively or adapted to Mirrorless, John Riley takes a look at the history and models of the compact SLR Pentax-M series of camera and lenses.

Posted: 15/04/2024 - 14:30


Fashions come and fashions go, then they repeat themselves in seemingly endless cycles. However, sometimes things come together in a way that drives real change and even real progress. So it was in the mid 1970s, when several disconnected technologies gelled together to make possible a whole new drive for compact, electronic SLR cameras and the lenses to go with them.

These new technologies included new plastics that were strong and stable, new batteries in Silver Oxide cells, new compact electronics, LEDs and Gallium and Silicon photo sensitive diodes. Most SLR cameras were large and heavy, some well designed, some clunky and Heath Robinson in their design ethos. To be fair, Asahi had been producing relatively small and certainly elegantly designed cameras for some time, culminating in the Pentax Spotmatic and then the three new K mount SLRs, the KM, KX and K2. That was to be just the beginning.

First off the starting grid was the Olympus OM-1, a new compact SLR that was brilliantly promoted despite its fairly ordinary specification and not even multi-coated lenses. But it was compact and elegant, the lenses lovely jewels and the whole system vast and endorsed by every major high profile photographer that could be found.

The time was right, and Pentax went for everything that a compact , or even a professional camera could be, and less...that is, less weight, less bulk but with all the new technology making it all possible. The M series was born.

The ME and MX

By May 1977 the first reviews of the new Pentax ME were hitting the shelves, the first of the new Pentax compact era. No longer did we have manual shutter speeds, just aperture priority. This was a radical move in many ways, but aperture priority had long been shown to work and had the major advantage that it worked whatever was put in front of the camera. The shutter was a vertical run metal focal plane design by Seiko with a huge range for its day of 8 seconds to 1/1000 second. The age of electronic control was here. Silver Oxide batteries would power the electronics and easily last for a year, even with the power hungry LED readout in the viewfinder that showed all the shutter speeds. New stabiliser circuits eliminated the annoying tendency for LEDs to flicker when the mirror flipped up. Although Pentax solved this problem, the first cameras with LEDs still had the issue. Altering the exposure for backlight or other unusual lighting was achieved with the exposure compensation dial, another first. The large viewfinder had a pentaprism coated with silver for maximum brightness, much better than using aluminium. A dedicated power winder managed 2fps and adapted the diminutive camera for larger hands. But for those who used the wind on lever there was a delightful tactile experience to be had, with the lightest, smoothest and most gorgeous feel known to humankind.

Pentax M Series Cameras

The MX had a different, lower profile but was just as compact. This sibling was a mechanical camera with a rubberised silk horizontally running shutter of conventional range, that is 1s to 1/1000s, with conventional tolerances to speed. So, the fastest speed could be 1/750s or even 1/1250s for example and be within the tolerance allowed of 20%. However, this was the norm for mechanical shutters of the day, although the advantage was that the shutter would operate without a battery. Exposure was via the same GPD (Gallium Photo Diode) cells as the ME, but this time with a green central LED for correct exposure and orange and red LEDs either side to indicate plus or minus one half of a stop and 1 or more stops. The same silver coating for the pentaprism, the same elegance of design and a different power winder, but also a full 5fps motor drive as well. The manual wind on was smooth enough, but with the different kind of shutter not in the category of sublime. The MX was the professional camera with a full range of appropriate accessories.

Following the huge success of the ME and MX, development of the ME continued and 1980 saw the introduction of the iconic ME Super, adding push button selection of shutter speeds to the ME design. The range was slightly altered to 4s to 1/2000s. In those days magazine tests included a speed check and time and again the new shutter delivered 0.5ms, or exactly 1/2000s, at the top speed, an unheard of accuracy.

The Low Cost Options

The MV and MV1 of 1980 were lower priced simplified versions of the ME, losing the self timer in the MV along with exposure compensation and full readout in the viewfinder. Instead, a red LED meant over exposure so close down the aperture till a green light meant correct exposure. A orange light meant a long shutter speed so advised the use of a tripod. Exposure compensation was achieved by changing the ASA value, a bit laborious but it does work. The MV1 has a winder connection and also a self timer, but otherwise is the same as the MV.

The MG of 1981 relented a little and also reinstated a full readout of shutter speeds, but is otherwise an MV1.

The Arrival of AF

The last development is the ME-F of 1981, a camera which is basically an ME Super and can be used as one. Add the special 35-70mm f/2.8 Autofocus lens though and it becomes an effective but relatively slow autofocus camera. AF is only possible with its dedicated lens, which carries its own AF motor and power supply. The ME-F itself uses four silver oxide batteries instead of two, and these are found behind a quite vulnerable plastic door on the camera base. Non-AF lenses can be used in the usual way, with the helpful addition of the focus indicator of the ME-F body. This comprises horizontal arrows in the viewfinder that indicate which way to turn the focusing ring to achieve the point of focus. The central green LED marks the spot. Although the ME-F as an AF design may have been a dead end, nonetheless it remains an important first step for Pentax into the autofocus world.

Pentax M Series Cameras
Designation Modes Shutter range EV range Weight Notes and comments
MX 1976 Manual 1-1/1000 1-19 495g Mechanical camera
ME 1976 Auto only 8-1/1000 1-19 460g Exposure compensation dial
ME Super 1980 Auto Manual 4-1/2000 1-19 445g Exposure compensation dial
MV 1980 Auto only 1-1/1000 3-19 420g No self timer
No auto winder
Limited viewfinder info
No exposure compensation dial
MV1 1980 Auto only 1-1/1000 3-19 425g Limited viewfinder info
No exposure compensation dial
MG 1981 Auto only 1-1/1000 2-19 425g No exposure compensation dial
ME-F 1981 Auto/Manual 4-1/2000 1-19 480g Autofocus with SMC Pentax-AF 35-70mm f/2.8 lens. Version of ME Super

The M Series Lenses

For this writer, the M series lenses represent the pinnacle of the meeting of high quality, compact size and pure elegance of design, the last hurrah of metal over plastic with the electronic A series not yet on the horizon. It can be happily conceded that Pentax were not alone and both they and Olympus produced a gorgeous range of lenses with beautiful handling and delightful aesthetic appeal just as objects of beauty in their own right. Not all of them maybe, but there are many examples within the M series range that have their fair sprinkling of that “pixie dust” that we can recognise in an image but which is beyond the bald measurements of technical tests.

Pentax M Series Lenses

Not all the bayonet lenses made it into the M series compact lens range. For example the SMC Pentax 15mm f/3.5 and SMC Pentax 50mm f/1.2 lenses went straight to the A series, presumably because the design could not be so readily adapted to the new compact requirements. New designs did appear, and the ultra-compact SMC Pentax-M 40mm f/2.8 “Pancake” lens must surely be the star of the show. As well as making a pocketable match with the Pentax ME it was a stellar performer.

The M series eventually gave way to the A series with its electronic contacts that enabled shutter priority and program modes and eventually a pathway to the DSLRs that we enjoy today, but for the sheer pleasure of using a manual focus vintage/classic lens, the Pentax M series is arguably unsurpassed.

Pentax M Series Prime Lenses
Specification Elements/Groups Min Focus Weight Filter Size Notes and comments
Ultra Wide
20mm f/4 8/8 0.25m 150g 49mm Very sharp, some barrel distortion
Wide Angle
28mm f/2 8/7 0.30m 215g 49mm  
28mm f/2.8 7/7 0.30m 156g 49mm  
28mm f/3.5 6/6 0.30m 180g 49mm  
35mm f/1.4 10/8 0.40m 420g 58mm Ultra-rare lens
35mm f/2 7/7 0.30m 206g 49mm  
35mm f/2.8 6/6 0.30m 174g 49mm  
40mm f/2.8 5/4 0.60m 111g 49mm Almost perfect drawing (-0.2%)
50mm f/1.4 7/6 0.45m 238g 49mm High contrast reportage lens
50mm f/1.7 6/5 0.45m 185g 49mm  
50mm f/2 5/5 0.45 165 49  
85mm f/2 5/4 0.85m 250g 49mm  
100mm f/2.8 5/5 1.00m 224g 49mm Superb optically
120mm f/2.8 5/5 1.20m 275g 49mm Soft wide open, sharp stopped down
150mm f/3.5 5/5 1.80m 290g 49mm  
Long Telephoto
200mm f/4 6/5 2.00m 400g 52mm  
*300mm f/4 8/7 4.00m 825g 77mm  
400mm f/5.6 5/5 5.00m 1220g 77mm  
2000mm f/13.5 6/4 20.00m 8000g BI/52mm Mirror lens
50mm f/4 4/3 0.234m 167g 49mm 1:2 Magnification
100mm f/4 5/3 0.45m 357g 49mm 1:2 Magnification
100mm f/4 Dental 5/3 0.45m 357g 49mm Dental Macro Lens kit
Pentax M Series Zoom Lenses
Specification Elements/Groups Min Focus Weight Filter Size Notes and comments
24-35mm f/3.5 9/9 0.50m 290g 58mm  
24-50mm f/4 12/10 0.40m 380g 58mm  
28-50mm f/3.5-f/4.5 10/10 0.60g 310g 52mm Some distortion
35-70mm f/2.8-f/3.5 7/7 1.00m 470g 67mm  
40-80mm f/2.8-f/4 7/7 1.20m 395g 49mm  
75-150mm f/4 12/9 1.20m 465g 49mm  
80-200mm f/4.5 15/12 1.60m 555g 52mm Version 1
80-200mm f/4.5 12/9 1.20m 615g 52mm Version 2
AF Lenses
35-70mm f/2.8 7/7 1.20m 580g 58mm AF lens for ME-F
32-39mm f/2.8 8/8 0.50m 230g 49mm No details known

M Series Technique with DSLRs

As the lenses have no electronic contacts and the DSLR cameras are missing mechanical linkages, there are some restrictions to using M lenses on a DSLR. When the camera is switched on it will ask for the focal length fitted, for the benefit of the Shake Reduction system. Set the aperture you want on the lens, focus the lens throught the viewfinder or on the back screen (Press the centre of the four way controller to magnify the Live View) and then press the green button on the back of the camera. The lens will stop down and the camera will measure the light and set an approriate shutter speed. Complete the exposure by fully pressing the shutter release. With just a little practice, this process is fast and reliable.

Reviewed M Series Lenses

For further reading John Riley has recently been putting some of the M Series lenses to test.

John Riley

My specialised interest in Pentax started from the first moment I looked through the viewfinder of my first Spotmatic, the SP1000. That gorgeous clarity, sharply defined within a pure black frame is my definitive way to view the world and make images. Pentax is a superb example of a range of manufactured tools that is both the path to creativity and also a gem of engineering elegance and excellence in its own right.

Biography Profile John Riley Photography

Members gallery photos using: smc PENTAX-M 50mm F1.7

Posted 21/04/2024 - 14:37 Link
The remark of the M 2.8/120 being soft is a mistake. This goes for the Super-Multi-Coated TAKUMAR and the equivalent smc Pentax lens. The M lens has a different optical scheme and is very good at wide apertures.

Gerjan van Oosten,
author of The Defenitive Asahi Pentax Collector's Guide 1952 - 1977
Posted 24/04/2024 - 00:21 Link
I hear you, but all I can tell you is that the copy of the 120mm I owned was indeed softer at wide apertures, and I didn't particularly like the lens. The comment is from my own experience, not received wisdom, although of course that was just one sample of the lens. So no mistake, just my opinion, and I am quite happy to accept that other copies of the lens may be better.
Best regards, John

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