Five Way 50mm PK Showdown

Some weeks back I experimented with four M42 50mm lenses to see how they compared shooting the same scene at a range of apertures.

The results were, at least in part, quite unexpected, and the all round victor was the wonderful Asahi Super-Takumar 55/1.8.

With that in mind, and with my 50mm lenses in Pentax K Mount multiplying like rabbits in springtime, I thought a similar showdown might be interesting, and helped me to thin the herd, or the, er “fluffle” if you’re reading in North Canada.

The Lenses

Auto Chinon 50mm f/.7. Very affordable, small, smooth, an overlooked genuine rival to the Pentax-M 50/1.7. Six aperture blades, min focus 0.45m.

SMC Pentax-A 50mm f/1.4. Far more expensive (2-3x) than the A or M 50/1.7. The most expensive PK 50mm I’ve ever bought. Eight aperture blades, min focus 0.45m. Smooth enough focus but plasticky aperture.

SMC Pentax-A 50mm f/1.7. Cheaper than the 50/1.4, generally a bit more than the M version, due to its additional program modes on compatible bodies. Six aperture blades, min focus 0.45m. Like its 50/1.4 sibling, a cheap feeling aperture ring (my example doesn’t go past f/8 either), but pretty smooth to focus.

SMC Pentax-M 50mm f/1.7. Optically like the A version, but more metal and as a result it feels much smoother in the aperture ring especially. Very classy. Six aperture blades, min focus 0.45m.

Ricoh Rikenon 50mm f/2. Small, very light, simple full stop plastic aperture ring, very affordable and plentiful. Six aperture blades, min focus 0.6m

The Experiment

Simple, as before, one scene that I might typically photograph anyway (rather than a brick wall or newspaper taped to a wall!) at close focus with enough light in the background to create bokeh highlights.

Because the Rikenon only focuses to 0.6m, I chose that distance for all of the lenses, not measured, just going by the scale on the lenses.

I shot wide open, then full stops to f/8, as I hardly ever shoot beyond this. Oh and I used my ever reliable Sony NEX 3N plus PK > NEX adapter, shooting RAW at ISO400 then converting to JPEG in LightRoom, my usual set up.

The Results

The simplest conclusion is obvious – any of these are an excellent option for a 50mm prime lens, not just in Pentax K mount.

Trying to differentiate between the images, at my level of analysis and requirements, was very difficult.

In terms of colours and contrast and sharpness, there’s so little between all the lenses, they’re close to identical.

Where I did notice differences was in the bokeh. 

The Pentax-A 50/1.4, to my eyes creates prettier images at nearly all apertures than all of the others, because it has extra aperture blades that make the bokeh highlights rounder, less aggressive.

The Pentax-M 50/1.7, A 50/1.7 and Auto Chinon 50/1.7 were virtually identical in every way, at all apertures tested.

If I mixed up the results I wouldn’t be able to tell you which lens took which picture. From this point on, there’s little point separating them in terms of optical performance.

At f/5.6 and f/8, the Rikenon 50/2 also was close to indistinguishable to the three above.

At wider apertures though, the Rikenon impressed more than the three 50/1.7s.

Though it also has six aperture blades, because its “only” f/2, at f/2 the bokeh highlights are perfectly circular whereas the others are starting to become hexagonal.

At f/4 this is becoming far more obvious, and in fact at this aperture the bokeh from the Rikenon is more appealing than the Pentax-A 50/1.4 too.

So how do I rate five lenses that performed so equally? 

It simply comes down to the fine detail, of the lenses themselves, and of the image.

Images first.

Wider than f/4 there’s so little between them all there’s nothing to discuss. At f/4 though, where I probably shoot more than at any other aperture, the Pentax-A 50/1.4 and Rikenon 50/2 I like most, because of the much smoother and less invasive bokeh.

At f/5.6 and f/8, the Rikenon becomes as hexagonal as the three f/1.7s. At these apertures, the 50/1.4 gives the most pleasing results, and the most subtle bokeh.

So on the image front, overall it’s the Pentax-A 50/1.4 first, Rikenon 50/2 second, the three 50/1.7s joint third.

Let’s turn to the spec and feel of the lenses. 

All five are a pleasure to use, to an extent. In terms of luxury and smoothness of feel, the Pentax-M 50/1.7 is the winner. Joint second are the Auto Chinon and Rikenon, and joint last the two Pentax-As, with their disappointingly flaky plastic aperture rings.

Spec wise, there’s very little difference, again.

The obvious standout (or rather fall down) is the Rikenon with only 0.6m close focus compared to all of the others going down to 0.45m. If Ricoh had made this lens focus down to 0.45m it could be the overall winner here, amongst illustrious company.

(Ricoh do make a 50/1.7 that focuses down to 0.45m, but whilst competent, I haven’t found it to be as good as the 50/2.)

The Pentax-A lenses of course have added electrical contacts so that compatible cameras can shoot Shutter Priority and Program modes.

If you use an A series or later Pentax film body and/or a Pentax DLSR this is legitimately a serious advantage to consider.

On my Sony NEX, with the same adapter and the same process of manually stopping down the aperture, the difference in using all five lenses is non existent.

The slower max aperture of f/2 on the Rikenon, plus the fact that it performs very well at this aperture, actually give it an edge over the f/1.7s, as explained in the bokeh quality above. 

The extra speed of the Pentax-A 50/1.4 in itself is redundant for my needs, and as I spoke about recently, we probably don’t need an expensive f/1.4 over an f/1.7 or f/2 on any level.

But what it does have that genuinely makes it stand out here are the extra aperture blades.

And for someone like me who shots up close very often, with a relatively shallow depth of field, this is a very important distinction. I wouldn’t care if it’s max aperture was f/2 (or even f/2.8), it’s those extra blades (and the shape they form) that make a difference.

Summary

If I was going to recommend just one of these lenses, I would advise you to use whichever you already have, or next come across. They’re all excellent.

For my needs and style, I can clearly see that I don’t need three 50/1.7s that are near identical.

If I used just M series Pentax film bodies, I’d pick the Pentax-M. It has the best feel of all the lenses here. 

If I used A series film bodies, and needed those extra exposure modes, I’d go with a Pentax-A lens. Same story with a Pentax DSLR – the A lens gives more exposure options, if you need that.

But coming back to my own requirements, this test has highlighted that against what I first thought – that the extra speed alone of the A 50/1.4 was not worth the extra expense – it’s this lens that appears to have triumphed.

I can live with that plastic aperture ring for the bokeh advantages.

For times when I want to be lazier and shoot an SLR (or DSLR) like a point and shoot with Program modes, it makes the most sense too.

The Rikenon is a little wonder, and I doubt I’ll let it go because it is so small, light, cheap and so good wide open. 

My first Pentax 50mm lens was a Pentax-M 50/1.7 and for a long time I’ve considered them the benchmark. Maybe for slightly nostalgic reasons I’ll be holding on this example, plus its undoubtable quality of build and feel.

The Chinon and Pentax-A 50/1.7s – as great as they are – offer simply too much duplication in my current collection, so will soon be sold on, leaving the A 50/1.4, Rikenon, and for now the M 50/1.7, to join my Pentax-M Macro 50/4 in PK mount at 50mm.

I considered including the Macro 50/4 this test, but with its much closer focus and max aperture of f/4 it’s too different to be a fair comparison, plus I love it so much it’s a no brainer keeper anyway.

No doubt that lens, plus the A 50/1.4 that’s triumphed here, will have their own Lens Love posts in the near future, and in all honesty are the only two lenses I need – or will ever need – in Pentax K mount.

Which is your favourite image of those above? 

Please let us know in the comments below.

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