SMC Pentax-M 50mm f/1.4 Lens Review

Superfast 50mm M Series vintage lens from Pentax. John Riley reviews this easily adapted, widely available f/1.4 classic, sharing sample photos, MTF & CA performance charts along with his verdict of this standard length K mount lens.

Posted: 23/10/2024 - 17:54

Handling and Features
Performance
Verdict
Specification

Described by the Pentax literature of its day as the "workhorse" standard lens, the SMC Pentax-M 50mm f/1.4 was manufactured from 1977 to 1984, after which it gave way to the A series version. Although slightly heavier and larger than the f/1.7 version, it is still miniscule compared to current 50mm lenses. Without the need for electronics and AF motors, the lens comprises just the glass and the metal framework that holds it all together. This was a quality lens in its day, so the question is, as always, can it stand up to the current superb options on the market and indeed can it deliver the goods when used with modern digital sensors rather than film? Armed with the 36MP Pentax K-1 full frame DSLR, let's venture out into the world and see how it all pans out.

SMC Pentax-M 50mm f/1.4 Handling and Features

First off, many thanks to Pentax User's very own Rick for providing the loan of his lens. It looks in splendid condition, which bodes well for it having been well cared for in its almost 50 years of exisitence. That a lens of this vintage can still be used on a current Pentax DSLR is a tribute to the forward thinking of the designers of the 1975 Pentax K mount.

We have no electronics here though, so using the lens requires the usual stop down metering and manual focus. It becomes essential to adjust the Pentax viewfinder settings properly (so the etched lines are sharpest) so that we can see and focus the image easily in the viewfinder. This is aided by a helpful bleep from the AF system if that is left switched on. However, when very high focusing accuracy is needed we need to use the Live View image with magnification. Be prepared to be amazed at how poor the human eye is at finding sharpest focus with a pentaprism viewfinder. This is why manual focus film cameras had focusing aids such as microprisms (image shimmers when out of focus) or split image central areas (lines are displaced when out of focus).

Our usual lens tour begins with the large front element and the conventional 49mm filter thread. Any 49mm thread standard lens hood can be used, rubber hoods being popular and useful for pressing up against glass for museum shots and the like. There are specific Pentax hoods, including a round screw-in one and the clip on square hood that is arguably the most convenient and efficient. Using a hood is definitely best practice, but the SMC (Super-Multi-Coating) flare resistance was excellent and remains excellent, so we can get away without a hood for many shots. This holds true for many of the prime lenses of this era, with perhaps only up to 7 or 8 elements to cause reflections, but is probably less true of highly complex zoom lenses.

The lens is compact, very compact by current standards, weighing in at 236g without hood and 252g with the square clip on hood, as measured. Pentax quote 238g in the literature. Dimensions are a svelte 63mm x 37mm. The manual focus ring is as usual ultra-smooth, and the sheer tactile pleasure of the Pentax system has been mentioned by this reviewer many times. Some other marques of the era were surprisingly stiff and/or notchy by comparison. Focusing is down to 0.45m (1.5 feet) for a maximum magnification of 0.15x.

The focusing scale is visible via a wide cutout, with feet clearly etched in blue and metres in yellow. The etching is of high quality and the paint infill clear but subtle. The very long throw of the focusing ring and the wide cut out mean that the provided depth of field scale is quite usable. There is an infra-red adjustment mark at the f/5.6 point, to indicate the focusing adjustment needed with IR film. Lenses of this era are generally not apochromatic, never mind IR corrected.

The aperture ring has positive and smooth click stops at f/1.4, f/2 and then half stops until we reach another full stop interval between f/16 and f/22. Finally, there is the high quality stainless steel K mount in its original plain version, without any electronics.

The metering process with the K-1 and other DSLRs is simple enough though. Switching on the camera, we are asked what the focal length is for the purposes of the shake reduction system. Then, with the mode dial set to M, select 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 selected value. This soon becomes second nature and makes the use of these fine lenses absolutely viable.

SMC PENTAX-M 50mm f/1.4 Sample Photos

Optical construction is 7 elements in 6 groups, with the diaphragm having 8 blades. The lens is Super-Multi-Coated, abbreviated by now to SMC in the lens description. This version of the lens was manufactured from 1977 to around 1984, after which it was replaced with the A series version, with electronic contacts and an “A” on the aperture ring. There is no denying that the A lens is more convenient to use on DSLRs because it links with the camera electronics and the exposure modes may be used as normal. However, the M series are less plasticky, maybe not exactly better made, but constructed with more metal and having a definite feeling of traditional quality that can be lacking on later offerings.

Using the M series lenses is quite an experience as in so many ways they are a pinnacle of ergonomic design, utterly slick and smooth in operation, compact and delivering (in the main) stellar results, on film for sure. On digital, some are equally excellent, some less so, which makes looking at them with the K-1 rather intereresting. The 50mm lenses appear to be in the category of stellar performers, so the question now becomes whether or not the original thoughts over the various merits of the f/1.4 and f/1.7 versions are still as true in 2024 as they were in 1977. The received wisdom is that the f/1.7 is the better performer, but the f/1.4 better suited to reportage, street and newspaper usage with a grittier, higher contrast at the expense of fine resolution. We shall see, so first then the technical performance and then the verdict.

SMC Pentax-M 50mm f/1.4 Performance

Central sharpness is very good at f/1.4, rising to being excellent between f/2 and f/16 and still very good at f/22. The edges are frankly poor at f/1.4 and f/2, very soft indeed, although for portraiture it could be argued this is a potentially useful feature. Edge sharpness is however very good from f/2.8 to f/16 and still good at f/22.

SMC PENTAX-M 50mm f/1.4 MTF Charts

CA (Chromatic Aberration) is centrally very well controlled, hovering around one quarter of a pixel width. CA does become very obvious at the edges, something that was not an issue on film, especially when shooting black and white. It did not shout out on colour slides either, so it may well be that the lack of telecentric design (where exit light rays are as parallel as possible) plus the nature of the digital sensor contribute to this substantially. However, most subjects do not really suffer because of this and there are always software solutions if needed.

SMC PENTAX-M 50mm f/1.4 Chromatic Aberration Charts

Distortion measures -1.24% barrel, very acceptable with this lens design.

Bokeh is the smoothness of the out of focus areas in an image, and in its day was not something often discussed, not having acquired the name yet. The bokeh sample shots below give the verdict on this.

SMC Pentax-M 50mm f/1.4 Versus f/1.7 - Bokeh & Sharpness comparisions

SMC PENTAX-M 50mm f/1.4 Aperture Range

Flare is not a problem in general shooting, but artefacts can be generated with strong light sources in the frame. The saving grace is that the lens can still see through the flare and the artefacts created could be multi-coloured and magnificent for a particular style of imagery.

Vignetting is pretty obvious wide open, but has cleared up to a moderate level by f/2.8.

Aperture	Vignetting
f/1.4	-2.3
f/2	-1.6
f/2.8	-1.2
f/4	-1.1
f/5.6	-1.1
f/8	-1.1
f/11	-1.1
f/16	-1
f/22	-1

Value for Money

Looking at eBay, there are plenty of BIN offers from £50 to £80, with plenty left unsold at the higher price levels, so there should be good potential for seeking out a bargain. This particular lens used for this review would probably command the higher end of the scale, being in beautiful condition.

Is this good VFM? Yes, certainly, with a classic imaging style all of its own. There is a price penalty to pay for a faster lens, but either way the VFM equation is sound.

SMC Pentax-M 50mm f/1.4 Verdict

The 50mm lens is a very, very useful optic to own. Every photographer could feel the need for a compact, fast, high quality lens that can ensure an image of most subjects can be captured. Carrying a 50mm is not a burden, and using one as a main lens even as an experiment is very rewarding, replacing zooming with using our feet to move around. It has been said before, but there are good solid reasons why the 50mm lens was the standard lens for a very long time, and even now survives as a major player in any manufacturers range.

Having established 50mm is a desirable option, which one to choose - f/1.4 or f/1.7? Trying them out on digital and shooting with both lenses, there are slightly different qualities to both, but at the end of the day it is a moot point which lens is "better". The prices are fairly similar, they will not disappoint, so probably the one to go for is the one that is in the best condition, with more emphasis on that than on the speed of the maximum aperture.

Another Highly Recommended M series lens.

• SMC Pentax-M 50mm f/1.4 Versus f/1.7
• SMC Pentax-M 28mm f/1.7 Lens Review
• SMC Pentax-M 28mm f/2.8 Lens Review
• SMC Pentax-M 135mm f/3.5 Lens Review
• SMC Pentax-M 75-150mm f/4 Zoom Lens Review

 

 

Specifications: SMC PENTAX-M 50mm f/1.4
General
Focal Type	Standard
Availability
Year announced	1977
Discontinued	Yes
Dimensions
Diameter	63mm
Height	37mm
Weight	236g
Construction
Groups	6
Elements	7
Blades	8
Lens
Maximum magnification	0.15x
Internal focusing	No
35mm equivalent	50mm
Stabilised	No
Filter Size	49mm
Min Aperture	f/22
Max Aperture	f/1.4
Focal Length	50mm
Focusing
Macro	No
Min Focus	45cm

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