John Riley reviews the beautifully crafted vintage SMC Pentax-M 28mm f/2.8 lens from the late 1970s early 80s. Read how a legacy lens from this era performs compared to modern standards, along with viewing sample photos, MTF & CA charts from testing this lens.
Posted: 04/01/2024 - 10:27
Handling and Features
Performance
Verdict
Specification
Following the introduction of the M series compact film cameras, initially the ME and MX of 1976, Pentax fairly promptly presented the new M series range of compact lenses. This SMC Pentax-M 28mm f/2.8 is a beautiful, mint example of the first model of this specification, manufactured from 1977 to 1982. In contemporary group tests of 28mm lenses it scored very highly, even outclassing some very prestigious names, and at a relatively modest cost. Of course film-era lenses, especially wide angles, may or may not perform well with digital sensors, but we start with a lens with an excellent reputation so, let's see where it leads us as we couple it up with the 36MP Pentax K-1 full frame body.
SMC Pentax-M 28mm f/2.8 Handling and Features
In common with the M series lenses generally, this is a beautifully compact but solidly made piece of optical manufacture. It looks like a small gem of engineering, and handles as slickly as we could possibly hope for. For a start, it is very compact, measuring just 63mm x 31mm and weighing in at a very modest 157g, as measured without hood or caps. There is a dedicated clip on lens hood, but one was not available at the time of this review. The filter thread is the usual 49mm, in common with most other M series small prime lenses.
The manual focusing ring has that gorgeous silky Pentax feel to it, and is a tactile pleasure in its own right. The focusing scale is in a cutout, and takes us down to 30cm (12 inches) for a maximum magnification of 0.12x. There is of course no AF in this era. There is a nicely spaced depth of field scale that is actually usable, and this includes an IR index mark in red, actually the f/4 index. For IR film, focus is made and then the distance moved to the IR mark, thus compensating for the fact that the lens focuses IR light at a slightly displaced distance to visible light.
The aperture ring has firm but smooth click stops at half stop intervals, with the exception of the widest and smallest ends, where the click stops are at full stop intervals (between f/2.8 and f/4 and f/16 and f/22). This is quite normal for Pentax manual focus lenses.
There is also a neat snapshot setting, selected by aligning the focusing ring at 10 feet (3m) and the aperture at f/8. These settings are infilled in red and give an ideal street photography setting with depth of field from just under 5 feet to infinity. We just point and shoot, ignoring whether or not the viewfinder image looks in focus.
One other refinement is the small white plastic bubble on the lens, which can be aligned by feel with the correct position for mounting the lens into the bayonet fitting on the camera. The bayonet mount itself is a high quality stainless steel that fits with firm precision on the K-1 as well as it does on every other model of Pentax K bayonet camera. It is a plain K mount with no electronic contacts, so the camera must be used in stop down mode to ensure correct stopping down of the lens.
The metering process with the K-1 and other DSLRs is simple enough. Switching on the camera, first it asks what the focal length is for the purposes of the shake reduction system. Then set the mode dial to M, set the aperture required on the lens and press the green button on the back of the camera. The camera will meter and set the appropriate shutter speed and when the shutter is released the lens will stop down correctly to the set value. This soon becomes second nature and makes the use of these fine lenses absolutely viable.
SMC PENTAX-M 28mm f/2.8 Sample Photos
Optical construction is 7 elements in 7 groups, a similar design being used by almost all manufacturers of the era, although with their own fine detail of course. There are just five blades to the diaphragm, so bokeh basically hasn't been invented at this stage, although the smoothness or otherwise of out of focus areas is apparent, even without a name.
This particular example of the lens is from the first model, made from 1977 to 1982 and recognisable by the silver ring on the front of the focusing ring and the 156g (actually measured at 157g) weight. The second version was made from 1982-1984 and has no silver ring and the 170g weight of the later A series lens.
Handling is simple and the controls are beautiful to operate, the lens being quite a pleasure to use. Focusing is easy enough even with DSLR viewfinders, but of course Live View and magnification can make it much more accurate. 28mm on full frame is usefully wide without creating too much distortion, especially as current tastes accept wide angle shooting more readily that they did in 1977. Whilst it is true that using an A series lens, with its A setting on the aperture ring, is more convenient, the M series lenses are definite classics and have a character all of their own.
SMC Pentax-M 28mm f/2.8 Performance
Central sharpness is very good at all apertures, rising to excellent at f/8. The edges do lag behind, being only fair at f/2.8 and f/4, but very good at f/5.6 to f/16 before dropping to just good at f/22. Considering that the lens is designed for film and does not have a telecentric design (where the light rays are kept parallel as they exit the lens) this is a very impressive result for a wide angle of its era.
SMC PENTAX-M 28mm f/2.8 MTF Charts
How to read our MTF charts
The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges.
The scale on the left side is an indication of actual image resolution and sharpness as LW/PH and is described in detail above. The taller the column, the better the lens performance.
For this review, the lens was tested on a Pentax K-1 using Imatest.
CA (Chromatic Aberration) is centrally very well controlled, but the edges do show a fair bit of colour fringing on difficult subjects, such as bare branches against a bright sky. This can be tackled in software, although for most subjects and for monochrome shooting it is not particularly obtrusive.
SMC PENTAX-M 28mm f/2.8 Chromatic Aberration Charts
How to read our CA charts
Chromatic aberration (CA) is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.
Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more.
For this review, the lens was tested on a Pentax K-1 using Imatest.
Distortion measures just -1.0% Barrel, which is very respectable for a wide angle lens.
Bokeh is the smoothness of the out of focus areas in an image, and in its day was not something aften discussed, even then not having a name yet. The 5 bladed diaphragm does few favours here and the bokeh is a little ragged. For those who use wide angle lenses stopped down for maximising depth of field, this will not be an issue.
SMC PENTAX-M 28mm f/2.8 Aperture Range
The SMC, Super-Multi-Coating was a revelation when introduced in 1971 and it was widely proclaimed that lens hoods were obsolete as a result. That of course is not really true, but initial enthusiasm can get a grip quite easily. The SMC coating has been surpassed in many ways, and even today's SMC will be somewhat different to what is found in this lens. It still gives a very good account of itself though and normal photography will not find a problem with flare. Artifacts can easily be created in severe tests, but this is a characteristic and can be used creatively. This is one of the reasons for using vintage lenses.
Vignetting is there to be seen, and again it is a characteristic that can be taken advantage of. It is particularly obvious at wider apertures, but never really goes away.
Aperture | Vignetting |
f/2.8 | -1.9 |
f/4 | -1.7 |
f/5.6 | -1.7 |
f/8 | -1.7 |
f/11 | -1.6 |
f/16 | -1.5 |
f/22 | -1.4 |
Value for Money
Looking at eBay, realistic sales have generally been less than £50, which is really an excellent price for such a useful and high quality lens. There are bargains out there from a variety of sources, so keeping a watchful eye out might find a really superb example for even less. Excellent value for money.
SMC Pentax-M 28mm f/2.8 Verdict
There is a real case for using beautiful vintage lenses like this, apart from anything else putting them to good use as they were intended is arguably far better than letting them languish in a drawer or case, with fungus happily digesting the glass. A good clean example will make excellent images and be a whole lot of fun in the process.
The M series 28mm f/2.8 may be better than generally thought, providing a good copy is obtained. Looking back at a large group test from 1982, the Pentax lens was amongst the top performers, along with Zeiss and Olympus, and out performed the Leica lens tested. It was priced then at £51, so finding one now for a similar price or less is quite a bargain.
There will be some who find the stop down metering to be inconvenient, there are some who may find the manual focus difficult, but if these basic handling features can be mastered then this is an excellent lens that has that magic ingredient of beautifully balanced imaging character. Images look great and the lens can wholeheartedly be Highly Recommended.
M Series Lenses:
- SMC Pentax-M 50mm f/1.7 Lens Review
- SMC Pentax-M 135mm f/3.5 Lens Review
- SMC Pentax-M 75-150mm f/4 Zoom Lens Review
SMC Pentax-M 28mm f/2.8 Pros
- Very good overall sharpness
- Compact and light
- Full frame format
- Excellent value
- Beautifully made
- Very pleasing imaging characteristics
- Generally good flare resistance
- Low central CA
- Modest distortion
- Lovely tactile handling
SMC Pentax-M 28mm f/2.8 Cons
- Manual focus
- Stop down metering
- Edge CA obvious
- Wider apertures soft at edges
- Visible vignetting
Specifications: SMC PENTAX-M 28mm f/2.8 |
||||
General | ||||
Focal Type | Wide | |||
Lens Mounts | Pentax K | |||
Availability | ||||
Year announced | 1977 | |||
Discontinued | Yes | |||
Dimensions | ||||
Diameter | 63mm | |||
Height | 31mm | |||
Weight | 156g | |||
Construction | ||||
Weather-sealed | No | |||
Groups | 7 | |||
Elements | 7 | |||
Blades | 5 | |||
Lens | ||||
Maximum magnification | 0.12x | |||
Internal focusing | No | |||
35mm equivalent | 28mm | |||
Stabilised | No | |||
Filter Size | 49mm | |||
Min Aperture | f/22 | |||
Max Aperture | f/2.8 | |||
Angle of View | 75° | |||
Focal Length | 28mm | |||
Focusing | ||||
Macro | No | |||
Min Focus | 30cm |
Members gallery photos using: smc PENTAX-M 28mm F2.8
There this old lens couldn't compare with slightly nwer designs like the Sigma 2.8/28 (which in the early 80's has been the test winner at the german Color foto magazin) or the much newer zoom-lenses.
But as nearly always:
those test shootings cannot hold up to real life photos where the ability to manual focus quickly and precisely is much better with the Pentax, where there is different light, not only a test chart but 3D-life-objects and so on.
If you enjoy the feeling of manual lenses of those days you may also take a look at the Tamron adaptall mount lenses that give a really good and sometimes stunning feeling of what was mechanically lens building in those days.
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