SMC Pentax 1:1.2/50 Asahi Opt. Co., Japan - a review of a classic fast lens

Lens Material SMC Pentax 1:1.2/50 Asahi Opt. Co., Japan especially for Radozhiva prepared Rodion Eshmakov.

Thank you for providing the lens for the preparation of the article Nadir Tulasheva.

The SMC Pentax 1.2/50 lens (hereinafter referred to as Pentax 50/1.2) is a classic ultra-fast standard lens for film SLR cameras. This kind of lenses were created for reportage photographers and were their "workhorses" before fast apertures appeared. universal autofocus zooms. The hero of this article has been produced since 1975.

Today, old fast fifty dollars are often considered as artistic lenses due to the picture with pronounced aberrations and the shallow depth of field of the imaged space, although at the time of their development, obviously no one thought about special bokeh or the “correct” soft effect - the main task of such a lens was to form on low-speed film, a bright image so that the photographer can use a reasonable shutter speed - aperture for the sake of light.

The apotheosis was, of course, Carl Zeiss Planar 50 / 0.7, created for purely pragmatic reasons - to shoot the far side of the moon with NASA spacecraft, but also managed to be useful for shooting Stanley Kubrick's film "Barry Lyndon" and some others.

More reviews of vintage 50-58mm f/1.2 lenses:

1. Nikon 50mm 1: 1.2 Nikkor
2. Nippon Kogaku Japan Nikkor-S Auto 1: 1.2 f = 55mm
3. Nikon Nikkor-S Auto 1: 1.2 f = 55mm
4. Nikon NIKKOR-SC Auto 1: 1.2 f = 55mm
5. Nikon Nikkor 55mm 1: 1.2
6. CANON LENS FD 50mm 1: 1.2
7. CANON LENS FD 55mm 1:1.2 SSC
8. CANON LENS FL 58mm 1:1.2 Canon Camera Co., INC.
9. MS VOLNA-8N 1.2 / 52
10. MINOLTA MD ROKKOR 50mm 1: 1.2
11. MINOLTA MC ROKKOR 1: 1.2 f = 58mm
12. Porst Color Reflex MC Auto 1: 1.2 / 55mm

Specifications:

Optical design - 7 lenses in 6 groups, type "double Gauss" / "Planar";

Focal length - 50 mm;
Relative aperture - 1: 1.2;
Aperture - iris, 8 petals, "blinking";
Aperture limits - 1:1.2–1:22, discrete setting in 1/2 EV steps;
The minimum focusing distance is 0.45 m;
Filter thread diameter - 52 mm;
Camera mount - Pentax K mount;
Mass - 385

Mechanical and optical design of the lens

Pentax 50 / 1.2 is made in the Pentax corporate style of the late 70s - 80s and does not differ in layout from many other 50 mm lenses of that era. The lens body is made entirely of metal except for the ribbed plastic insert on the focus ring. The lens is very small in size (about 50 mm long) - a simple optical design made it possible to make it compact, which cannot be said about modern high-quality high-aperture lenses, competing with each other in which of them will cause the intervertebral hernia of the photographer. Nevertheless, the length of the camera-lens bond when using a planar-shaped Pentax 50 / 1.2 for a SLR camera turns out to be much longer than in the case of using a sonnar-like 7artisans 50 / 1.1 on mirrorless.

On the lens you can find distance scales in feet and meters, aperture value marks and a depth of field scale with a mark for shooting in the IR range. The distance scale of the lens is not fully visible, but partially through a special cutout window in the body. What's funny, in this place, in the copy handed over to me, fragrant lubricant seeps abundantly, just like from some LZOS Industara-61. But the focusing ring at the same time has a very pleasant, light, but viscous move. The downside is a small angle of rotation of the ring - only ~180°. When using a lens at medium and long distances, it is difficult to focus wide open, I had many misses due to the fact that the position of the focal plane was too sensitive to a small shift in the focus ring. The minimum focusing distance (MFD) is 0.45 m - Pentax 50 / 50 does not stand out among other 1.2 mm lenses. On MDF, you can shoot any small things, but nothing like macro photography will work without additional devices.

The SMC Pentax 50/1.2 has an eight-bladed diaphragm with dark matte rounded blades. In the interval F/1.2–F/2, the shape of the hole is close to round, but then it takes the form of a regular octagon.

As you can see, when viewed through the lens, there is no pronounced yellow tint that is inherent in earlier lenses. SMC Takumar 50 / 1.4: in the SMC Pentax 50 / 1.2 scheme, lenses made of radioactive thorium glass are not used, which, due to self-irradiation, accumulate defects in the form of color centers and darkens.

Once again, I note that well-known lenses with pronounced radioactivity emit precisely because of the use of glasses with thorium dioxide in the composition, and not because of some kind of radioactive / thorium coating of lenses, as is often written on all forums.

The optics of the SMC Pentax 50/1.2 has a proprietary multilayer anti-reflection coating, denoted by the abbreviation "SMC" ("Super Multi Coated") in the name on the title ring of the lens. In the 1970s and 1980s, multilayer coating was still something not taken for granted, because different manufacturers came up with different beautiful (or ridiculous) names for their coatings. At the same time, these names can hardly say anything about the quality of the coating, only about the fact of its presence.

Most likely, the number of coating layers for this lens is no more than 2-3, since the transmission spectrum of the lens measured by me is very close in shape to the spectrum of the Rubinar 100/2 MS with the corresponding technological coating level.

Color distortion produced by a multi-coated lens is generally less noticeable than from single-coated optics. However, the complex shape of the transmission curve leads to the problem of ghosting, which is very difficult to deal with. An example of the transmission curve of a lens with very, very good coating in terms of color reproduction - here, and a single-coated lens - here.

The Pentax 50 / 1.2 lens has a Pentax K mount, and with the appropriate adapter, the lens can be mounted on some SLR cameras (Canon EF) and mirrorless cameras. The lens presented in this article came with an adapter for Canon EF, and, apparently, on full-frame SLR cameras, the frame of the rear lens of the lens touches the camera mirror, therefore it was previously cut with a needle file.

I was interested in what materials the lenses of the objective are made of - such an analysis helps to find out the technological level of the lens, to understand how great the potential of the optical design is when using modern materials. I did not disassemble the entire lens for the sake of this, but conducted a non-destructive X-ray fluorescence analysis on a Bruker M1 Mistral spectrometer for the front and rear lenses.

The measurements performed for the front lens demonstrated the presence of significant amounts of lanthanum (La), barium (Ba), tantalum (Ta), niobium (Nb), tungsten (W) in the glass. The detection of zirconium (Zr) and tin (Sn) in this case is unreliable, since it is related to the hardware feature of the equipment. Thus, the front lens is made of lanthanum glass, which rather belongs to the group of so-called. "tantalum flints", having a refractive index usually from 1.77 to 1.9. In the Hoya catalog these glasses are called TAF (Tantalum Flint) and TAFD (Tantalum Flint Dense). This particular glass, rather, has a refractive index of about 1.8.

The analysis of the rear lens of the objective revealed the presence of lanthanum (La), gadolinium (Gd), tantalum (Ta), germanium (Ge), small amounts of niobium (Nb), arsenic (As) and lead (Pb). Thus, this glass most likely also belongs to the category of tantalum flint (TAF). At the same time, due to the lower content of niobium and tantalum relative to lanthanum and the absence of tungsten, this glass should apparently have a lower refractive index compared to the material of the front lens.

On the Web, you can find a patent similar to the SMC Pentax 50 / 1.2 lens (but not identical to it), also developed by Asahi, but much earlier - in 1966 - US 3451745. The lens described in it has a similar seven-lens layout and clearly differs from the serial one in the shape of the rear lenses. It is interesting that tantalum glasses TAF1, TAF2 and TAF1.8 glass, which is considered to be highly refractive (n>3), have already been used in this lens. Probably, the choice of materials in a serial lens is at least similar.

At one time, the so-called "tantalum" glasses made a small revolution in optics, making it possible to abandon thorium-containing materials in the development of high-aperture systems and zoom lenses. Moreover, some brands openly indicated in their advertisements about the use in the lens tantalum glass. Similarly, in the names often "shone" lanthanum.

Thus, the SMC Pentax 50 / 1.2 is made at a good technological level, but even inexpensive modern Chinese lenses, sometimes made according to a similar optical design, use much better glass brands, which cannot but affect the quality of optical distortion correction and lens image.

Optical properties

Wide open and up to F/2.8, the lens exhibits noticeable spherochromatic distortion, which manifests itself as a strong (at F/1.2) soft effect with colored (purple green) fringes. Up to F / 2.8, higher-order spherical aberration and field distortion (coma) are also quite strong, really good quality in the field is achieved with an aperture of no more than F / 5.6, and even at F / 11 some lateral chromatism will remain (colored rims of purple /green at the edge of the frame). For technical quality, the lens should be used at ~F/2, while pattern features are best seen, on the contrary, at F/1.2–F/2 (obviously).

SMC Pentax 50/1.2 has a good image contrast, behaves quite well in the backlight. I did not notice any problems with color reproduction, in general, the result obtained is predictable and manageable.

In terms of image quality, the lens is very similar to a huge number of other 50-58mm F / 1.4-F / 1.2 lenses, but in terms of picture and bokeh, it is definitely average at least. The main defect in the pattern is strong spherochromatism, due to which the out-of-focus disks have a bright green border and a red tone in the central part.

Comparison of optical quality and pattern of SMC Pentax 50/1.2 c Zenitar 50 / 0.95 и 7artisans 50 / 1.1 given in this article.

SMC Pentax 50 / 1.2 has a fairly high level of vignetting. Together with the poor image quality at wide aperture, this makes it unsuitable for use with cameras with a 44x33mm sensor. I used the lens on a full frame mirrorless camera Sony A7s с shift adapter to take pictures of an area similar to digital medium format and observed the appearance of dark corners in the image. Sample pictures are shown below.

The following are photos taken on Sony A7s without using a shift adapter.

All major versions of similar lenses Asahi Opt. Co., Takumar / Pentax:

1.2/50

1. SMC PENTAX 1: 1.2 / 50 ASAHI OPT. CO., JAPAN (7/6, 20947, 1975-1984)
2. SMC PENTAX 1:1.2/50 ASAHI OPT. CO.,JAPAN'GOLD' (7/6, 1981)
3. SMC PENTAX-A 1: 1.2 50mm (7/6, 20987, 1984-2004)
4. SMC PENTAX-A 1: 1.2 50mm Special (7/6, 2000)

1.4 / 50 (video)

1. Super takumar 1: 1.4 / 50 Asahi Opt. Co., Lens made in Japan (8/6, 358, 1964-1966)
2. Super takumar 1: 1.4 / 50 Asahi Opt. Co. Lens made in japan (7/6, 37800, 1965-1971, F/2 in number)
3. Super takumar 1: 1.4 / 50 Asahi Opt. Co. Lens made in japan (7/6, 37801, 1965-1971, F/2 dot)
4. Super takumar 1: 1.4 / 50 Asahi Opt. Co., Lens made in Japan (7/6, 37802, 1965-1971, comma after 'CO.')
5. Super-Multi Coated TAKUMAR 1: 1.4 / 50 ASAHI OPT. CO., JAPAN (7/6, 37902, 1971-1972)
6. SMC TAKUMAR 1: 1.4 / 50 ASAHI OPT. CO., JAPAN (7/6, 37908, 1972-1975)
7. SMC PENTAX 1: 1.4 / 50 ASAHI OPT. CO., JAPAN (7/6, 20847, 1975-1977)
8. SMC PENTAX-M 1: 1.4 50mm ASAHI OPT. CO., JAPAN (7/6, 20867, 1977-1984)
9. SMC PENTAX-A 1: 1.4 50mm (7/6, 20887, 1984-1989)
10. SMC PENTAX-F 1: 1.4 50mm (7/6, 20827, 1987-1991)
11. SMC PENTAX-FA 1: 1.4 50mm (7/6, 20817, 1991-2023)
12. HD PENTAX-D FA * 1: 1.4 50mm SDMAW (15/9, 21260, 2018->)
13. SMC PENTAX-FA 1: 1.4 50mm Classic (7/6, 2023->)
14. HD PENTAX-FA 1: 1.4 50mm (7/6, 2023->)

1.8 / 55 (video)

1. takumar 1:1.8 f=55mm Asahi OPT. CO., Japan (6/5, 1958, zebra)
2. Auto-takumar 1:1.8 f=55mm Asahi OPT. CO., Japan (6/5, 1958-1960, zebra)
3. Auto-takumar 1:1.8/55 ASAHI OPT. CO., Lens made in Japan (6/5, 1960, with 'R')
4. Auto-takumar 1:1.8/55 ASAHI OPT. CO., Lens made in Japan (6/5, 1960-1962, no 'R', oblique lines of the depth of field)
5. Auto-takumar 1:1.8/55 ASAHI OPT. CO., Lens made in Japan (6/5, 1962, no 'R', straight lines of depth of field)
6. Super takumar 1: 1.8 / 55 Asahi Opt. Co., Lens made in Japan (6/5, 1962, fine ribs, f/1.8 left)
7. Super takumar 1: 1.8 / 55 Asahi Opt. Co., Lens made in Japan (6/5, before 1965, fine ribs, f/1.8 right)
8. Super takumar 1: 1.8 / 55 Asahi Opt. Co. Lens made in japan (6/5, 37106, before 1971, large ribs)
9. Super-Multi Coated TAKUMAR 1: 1.8 / 55 ASAHI OPT. CO., JAPAN (6/5, 37104, 1971-1972)
10. SMC TAKUMAR 1: 1.8 / 55 ASAHI OPT. CO., JAPAN (6/5, 37108, 1972-1975)
11. SMC PENTAX 1: 1.8 / 55 ASAHI OPT. CO., JAPAN (6/5, 20747, 1975-1977)

2 / 55 (1.9 / 55)

1. Auto-takumar 1:1.9 f=55mm Asahi Opt. Co.,Japan (6/5, 1958-1959)
2. Auto-takumar 1: 2 f = 55mm Asahi Opt. Co., Japan (6/5, 1958-1959, zebra)
3. Auto-takumar 1: 2 f = 55mm Asahi Opt. Co., Japan (6/5, 34100, 1958-1959)
4. Super takumar 1: 2 / 55 Asahi Opt. Co., Lens made in Japan (6/5, small fins, F/2 left)
5. Super takumar 1: 2 / 55 Asahi Opt. Co., Lens made in Japan (6/5, small ribs, F/2 on the right)
6. Super takumar 1: 2 / 55 Asahi Opt. Co. Lens made in japan (6/5, 37103, 1962-1973, large ribs)
7. Super takumar 1: 2 / 55 Asahi Opt. Co. Lens made in japan (6/5, 37107, additional aperture pins)
8. SMC TAKUMAR 1: 2 / 55 ASAHI OPT. CO., JAPAN (6/5, 37109, 1973-1975)
9. SMC PENTAX 1: 2 55mm ASAHI OPT. CO., JAPAN (6/5, 1976-1977)

1.7/50

1. SMC PENTAX-M 1: 1.7 50mm ASAHI OPT. CO., JAPAN (6/5, 20877, 1977-1984)
2. SMC PENTAX-A 1: 1.7 50mm (6/5, 20897, 1984-1989)
3. SMC PENTAX-F 1: 1.7 50mm (6/5, 20837, 1987-1991)
4. SMC PENTAX-FA 1: 1.7 50mm (6/5, 20907, 1991-2004)

2/50

1. SMC PENTAX-M 1:2 50mm ASAHI OPTICAL CO. (5/5, 20677, 1979-1985)
2. SMC PENTAX-A 1: 2 50mm (5/5, 20697, 1985-1998)

2.2/55

1. takumar 1:2.2/55 Asahi Opt. CO., Japan (6/5, 1961-1963)
2. Auto-takumar 1:2.2/55 ASAHI OPT. CO., Lens made in Japan (6/5, 1961-1963)

2/58

1. takumar 1:2 f=58mm Asahi Opt. Co., Japan (6/4, 1957-1958)
2. takumar 1: 2 f = 58mm Asahi Opt. Co., Japan (6/4, 1957-1958, labeled 'R')

DA (APS-C: 1.4/55 DA* + 1.8/50 DA)

1. SMC PENTAX-DA * 1: 1.4 55mm SDM (9/8, 21790, 2008->)
2. SMC PENTAX-DA 1: 1.8 50mm (6/5, 22177, 2012->)

Asahi-Kogaku (M37x1, 3.5/50 + 2.4/58 -> M42)

1. takumar 1: 3,5 f = 50mm Asahi-kogaku (4/3, 1952, M37×1)
2. takumar 1: 3.5 f = 50mm Asahi-kogaku (4/3, 1952, , M37×1, pre-set)
3. takumar 1: 2.4 f = 58mm Asahi-kogaku (5/3, 1954, M37×1, silver)
4. takumar 1: 2.4 f = 58mm Asahi Opt. Co., Japan (5/3, 1957-1958, M42)

The lens names in this list correspond exactly to the lens name label on the lens barrel (except for the serial number and/or filter diameter).

Conclusions

The SMC Pentax 50/1.2 is a good old fast lens. First of all, it is of interest to owners of SLR cameras and to connoisseurs of the SMC Takumar 50 / 1.4 type of optics, who want more aperture and without the difficulties associated with the presence of thorium in the lens. And for mirrorless cameras, there are a huge number of modern manual lenses that are more attractive in terms of parameters, image quality and pattern.

You will find more reviews from readers of Radozhiva here.