If I am not shooting a Half Frame Camera, there is an overwhelming probability that I am shooting a Pentax instead. I have been shooting with Pentax 35mm SLRs for a long time and there are numerous reasons why they are my favorite 35mm SLRs. In fact, I’ve been working on a project espousing my love for Pentax, it’s called Gentleman Prefer Pentax.

Hopefully, it will end up like some sort of Herb Keppler meets “The most interesting man in the world” mashup but it may turn out to be absolutely nothing. I’m ok with that, I’m trying to be more comfortable with failure every day.

Anyways, I did this lens comparison a few weeks back and wanted to share the results with you. Here’s how it breaks down:

Why this comparison?

I get tired of people saying things like “The [insert any lens here] is just a dog but the [insert any lens here] is brilliant” OR “the [insert any lens here] is so much worse than the [insert any lens here]” OR “The bokeh on the [insert any lens here] is too distracting”…

This problem is not unique to Pentax. Cruise around photography forums and you will see similar statements about Nikon, Canon, Minolta, Olympus, etc., lenses as well. All of these statements are wrong, but some are less wrong than others.

Everything is in the eye of the beholder. This test is for me to see what I like best and you to see what you like best. And guess what? We may have different opinions, which is great! Variety is the spice of life.

I ended up with a copy of the SMC Pentax-M 50mm f/1.4 quite by accident and it made me think. I had used the 50mm f/1.7 forever and never really had a desire to seek out the 50/1.4 Why? I mostly shoot street and landscape. I could not give a damn about how the bokeh looks or how sharp the lens is wide open.

I shoot between f/5.6 and f/11 90% of the time and guess what? Almost every lens is sharp at those apertures. Nonetheless, I was intrigued by the possibility of the 50/1.4 being “better” than my 50/1.7, so I decided to conduct a little experiment.

Methods, materials and madness(s)

My Pentax ME Super + lens family
My Pentax ME Super + lens family

I started by grabbing my SMC Pentax-M 50/1.4, SMC Pentax-M 50/1.7 and SMC Pentax-A 50/2. I set them on the picnic table to take a picture of them and said to myself, why don’t I throw in the SMC Pentax-M 40/2.8 pancake and SMC Pentax 55/1.8 in the mix just for fun? So I did.

Five lenses in total, then:

  1. SMC Pentax-M 40mm f/2.8 pancake
  2. SMC Pentax-M 50mm f/1.4
  3. SMC Pentax-M 50mm f/1.7
  4. SMC Pentax-A 50mm f/2
  5. SMC Pentax 55mm f/1.8

I loaded up my trusty Pentax ME Super (probably my favorite aperture priority camera of all time) with some Fuji Superia 400 (which is my favorite 400 ASA budget color negative film right now) and got down to business.

I would start by shooting a straightforward scene of some plants and whatnot on my front patio. The lighting was ok. The camera metered the scene at 1/250 sec and f/8. I set it to manual after metering and took some shots, using a tripod to ensure the camera didn’t move while I swapped out lenses. Let’s call this Scene 1.

Next up, I found a side lit scene with a few geranium blossoms to focus in on. There was plenty of foliage and diffraction in the background making the scene an ideal one to test bokeh.

I again utilized a tripod to ensure a measure of consistency. I opened up each lens wide open with the camera in Aperture priority mode. This resulted in a bit of overexposure at the widest apertures, but with color negative film, the results are generally acceptable.

Finally, I stopped each lens all the way down to f/5.6, letting the camera decide on the shutter speed, before swapping out lenses. This resulted in a varying number of shots with each lens: Three shots with the 40/2.8, five shots with the 50/1.4 and four shots with everything else.

Here are the results.

Results: scene 1 – boring consistency

As above, the order of the lenses in the gallery above is:

  1. SMC Pentax-M 40mm f/2.8 pancake
  2. SMC Pentax-M 50mm f/1.4
  3. SMC Pentax-M 50mm f/1.7
  4. SMC Pentax-A 50mm f/2
  5. SMC Pentax 55mm f/1.8

Honestly though, the shots are complete sh*t and do nothing to help compare the sharpness of the lenses, especially with a low-resolution scan. (Mental note: Next time you test lenses, spring for the high-res scans so you might be able to actually see the differences).

Still, it’s entirely possible that at this aperture there are actually no differences at all.

Two things that jump out to me are:

  1. The differences in field of view between the lenses. 40mm seems quite a bit wider than 50mm, look at the powerline and sky to see how big of a difference there is. The shots are not interchangeable by any means. The disparity between 50mm and 55mm, while still noticeable, is not as significant. I am pretty sure you could pass off the 55mm shot as a 50mm lens and no one would notice without something to compare it to.
  2. The shot taken with the 50mm f/1.7 is underexposed and by at least a stop or three. How does something like that happen? The camera settings didn’t change…I am guessing it has something to do with the aperture blades not opening/ closing properly resulting in the underexposure…or possibly the electronic shutter on the ME Super was no bueno???

Time to try scene two.

Results: scene 2 – bokeh time

While not a perfectly composed image by any stretch of the imagination, it succeeded in its intended goal of highlighting the differences between each lens. And the differences between the lenses were more significant than I had imagined. I should say I was also really surprised by some of the results.

It’s worth noting here that people have varying opinions as to what the ideal bokeh is. Some people want bountiful bouncing bubbles, some people want swirls that twist and twirl, some people want butter smooth creamy goodness. More than that, one person may want one thing for certain shots and another for something else. Therefore any conclusions I draw here could be significantly different than your own…

SMC Pentax-M 40mm f/2.8

This is the smallest lens of the test. Attached to the diminutive ME Super it makes for an almost pocketable package which is really nice. Some people find the 40mm focal length a little awkward. It definitely requires that you get a little closer to your subject in order for it to stand out.

It’s also worth noting is that because of the compact design the focus and aperture adjustment rings are smaller than normal, making it a little more cumbersome when you are in a hurry to grab a shot.

SMC Pentax-M 40mm f/2.8 @ f/2.8:
Both Flowers are in focus. The background seems pretty neutral save for a few circular points of light in the upper right portion of the picture and just lower left of the flowers. Some of the areas meant to be in the background are almost in focus too. Specifically the branch above the flowers and the foliage on either side of the flowers. Despite this, there is still a bit of subject separation.

SMC Pentax-M 40mm f/2.8 @ f/4:
Similar to above with an even greater portion of the image in relative focus, yet the subject appears separate from the background.

SMC Pentax-M 40mm f/2.8 @ f/5.6:
An even greater portion of the frame is in focus now. DOF increased as expected. Subject and nearby foliage have merged into a single subject. Fenceline is now the background along with plants further back in the frame.

SMC Pentax-M 50mm f/1.4

The only lens here with 7 blades. In theory, this should produce the best-looking bokeh. I have heard people complain of the build quality on this lens and while it’s certainly not bad, it’s doesn’t feel as precise as the 50mm f/1.7 or 55mm f/1.8, just a bit more jiggly.

SMC Pentax-M 50mm f/1.4 @ f/1.4:
Oddly enough the front flower is more in focus than the last two shots and is starting to stand out in the frame. The background is a wild amount of circular bokeh.

SMC Pentax-M 50mm f/1.4 @ f/2:
Front flower is perfectly in focus, clearly separated from the background. Bokeh remains circular, less distracting.

SMC Pentax-M 50mm f/1.4 @ f/2.8:
Both flowers starting to come into focus. Subject separation still present. Bokeh remains circular.

SMC Pentax-M 50mm f/1.4 @ f/4:
Both flowers now in focus and clearly separated from the image. Background bokeh has receded.

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SMC Pentax-M 50mm f/1.4 @ f/5.6:
A common theme at this point: Both flowers in good focus, background elements starting to snap into focus. Bokeh small and circular.

SMC Pentax-M 50mm f/1.7

This has been my main lens for the last 3 years. It’s ubiquitous. It has come attached to the majority of Pentax cameras I have purchased throughout the years, it must have been their kit lens 😉 I always have 2 or 3 copies lying around and I use the same one to test on my newly purchased Pentax cameras.

SMC Pentax-M 50mm f/1.7 @ 1.7:
Like the 50mm f/2, the subject is only partly in focus at best. The background is full of round bokeh balls.

SMC Pentax-M 50mm f/2.8:
The front flower is in focus and the rear flower is partially in focus. Both achieve good separation from the background. Circular balls have turned to hexagonal shapes.

SMC Pentax-M 50mm f/4:
Both flowers in focus. Good subject separation. Bokeh has become smaller and more hexagonal

SMC Pentax-M 50mm f/5.6:
Still good subject separation, though some of the background is coming into focus as well. Bokeh is even smaller still hashave reverted to a more circular quality.

SMC Pentax-A 50mm f/2

This lens feels really good in the hand. It’s lightweight and balances better than the other lenses in the test. Definitely a different build quality than the rest of the lenses here. It’s the only SMC A lens, meaning it works in Program mode with more advanced cameras. It’s also a newer lens and as such has a more plasticky feel to it.

I bring this lens every time I travel out of the country or to unsavoury places (usually attached to a beat up old Pentax Super Program) because it doesn’t attract any attention and shoots in program mode allowing me to shoot really quickly.

SMC Pentax-A 50mm f/2 @ f/2:
I am not sure anything is in focus in this pic, maybe just a portion of the lower left flower and even that is suspect. As a result subject separation is poor. The really out of focus areas have numerous balls of light in the background.

SMC Pentax-A 50mm f/2 @ f/2.8:
Not much better than the previous shot although more of the front flower is in focus. Still numerous “bokeh balls” in the background with mild hexagonal element to them.

SMC Pentax-A 50mm f/2 @ f/4:
Finally, the subject is in focus. Background areas have been tamed down a abit. Still some noticeable hexagonal points of light in the top right portion of the image. Subject separation is clear at this point.

SMC Pentax-A 50mm f/2 @ f/5.6:
The entire subject in focus. A few pieces of background foliage are now more in focus as well. Subject separation still clear. Bokeh has calmed down further, providing less distraction. Whole image appears darker than previous images.

SMC Pentax 55mm f/1.8

I have had a bit of a strange fascination with this focal length since it came attached to a Pentax Kx I picked up a while back. It’s a bit of an odd duck compared to the rest of my Pentax lenses (52mm filter size…did Nikon make this thing?)

It’s slightly more cropped field of view seems to suit my style well, as it allows you to shoot from a little further away and get some nice separation between subject and background.

SMC Pentax 55mm f/1.8 @ f/1.8:
I’m kinda sounding like a broken record at this point but the front flower is almost in focus. The background is a blur of circular-shaped bokeh.

SMC Pentax 55mm f/1.8 @ f/2.8:
The front flower is fully in focus, the rear flower is starting to snap in as well. Subject separation is good. Bokeh has become more hexagonal.

SMC Pentax 55mm f/1.8 @ f/4:
Both flowers are now more in focus. Subject separation is clear. The background has calmed down and remaining bokeh balls are small and hexagonal.

SMC Pentax 55mm f/1.8 @ f/5.6
Again, background elements are starting to come into focus at this point but subject separation remains clear. Background more out of focus at this focal length than the others.


I’m not sure what to make of all this really… Scene 1 provided little if any information about distortion, chromatic aberration, sharpness. It only really showed the difference in field of view. It was kind of a waste of film, all things considered. Scene 2, however, did provide a bit of insight into how the lenses work with subject separation, background focus and the ever important subject of bokeh.

It also showed how hard it is to nail focus wide open. I shot these images on a tripod, there was a slight breeze. That was apparently enough to pull the subject right out of focus on some of the shots. Also, by f/5.6 all the lenses are pretty similar, especially the 50’s – just look below. Can you tell which is which without scrolling back up?

The 40mm doesn’t really belong in this test and was added as an afterthought. It has the least subject separation and things are never too far out of focus. Wide open at f/2.8, there isn’t really much bokeh to speak of. What little bit there is, has a nice round character and in general, the out of focus areas are pretty neutral. They neither add to nor detract from the picture.

This lens doesn’t achieve the same level of separation between subject and background in comparison to the other lenses which could be an advantage depending on your subject matter. I believe I could take street shots with this thing at f/5.6 all day long, and the results would be good.

The SMC Pentax-M 50mm f/1.7 has been my go-to lens for the last 3 years. That’s why it pains me so much to say that I was least impressed by the results. Wide open, the bokeh is fine but the out of focus areas are just a bit too chaotic for me. At f/2.8 it’s more hexagonal than the 50mm f/2. One of my favorite things about Pentax lenses is their half-stop aperture adjustments. It annoys me that I didn’t take a shot between f/1.7 and f/2.8 just to see what it would have looked like.

I think the SMC Pentax-A 50mm f/2 looked better both wide open and stopped down. While it still exhibited a hexagonal quality, it was tame in comparison to the 50mm f/1.7. Couple that with its lower price, lighter weight and the way it balances on a small Pentax body like the ME Super or MX, it’s one to keep around.

Lastly, the SMC Pentax-M 50/1.4. In practice, it’s a little too wild wide open but once you stop it down to f/2 things look really good, especially if you dig the bubbly type of bokeh. In fact, the nice circular bokeh balls are visible all the way up to f/4. I think this lens at f/2.8 might be my favorite image of the whole test and would be a clear choice if bokeh was your thing.

…but it’s not my thing, at least not with any of my current projects. It also doesn’t feel as good as the other lenses. The lens’ focus isn’t as crisp and the aperture ring doesn’t click the same way. It’s worth a bit more than the others so I will probably sell it on eBay sometime soon

The 55mm has the best out of focus areas and most subject separation regardless of aperture. I think it’s the best looking wide open of the whole test and although things get hexagonal rather quickly, the entire series of shots look pretty good. The out of focus areas never get too crazy in comparison to the 50mm f/1.7 and 50mm f/1.4.

If I wanted to shoot portraits, but still wanted a focal length I could walk around with, this would be my choice.

Suggested changes next time

  • Higher res scans
  • More parallel lines in Scene 1 to test distortion
  • More diversity of scenes to test sharpness, contrast, etc
  • Pick a scene with subjects a bit further away and not a subject under the influence of wind.
  • Skip f/5.6 there isn’t a big enough difference.
  • Maybe actually take a picture of a person too.

Now if you had to pick one lens which one would it be? Did you find this experiment helpful? What would you differently given the opportunity? (you do have the opportunity 🙂 )

I am working some other experiments right now. Let me know if you have any ideas you would like me to test.


~ Dan

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About the author

Avatar - Dan Marinelli

Daniel Marinelli

My name is Dan Marinelli. I am from San Diego, CA... where I work as a registered nurse and if I'm not working I'm either surfing, climbing/hiking or reading a book.…


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  1. Thanks for this review.
    Actually i’m comparing a similar set, the SMC-M 50mm f1.7, the SMC-M 50mm f1.4 and the SMC-A 35-70mm f4 on Pentax ME, ME Super, P30 and Program A.
    You can set this zoom to 40mm exactly, i like this 40 mm focal length, and the results are wonderful.
    Furthermore this 35-70mm zoom features a very near focus, around 0.4m at 40mm or 0.25 m at 70mm.
    Until now i used for standard purposes the SMC-M 50mm 1.7 only.
    But i’m interested in background blur and in low light photograpy, so i purchased the SMC-M 50mm f1.4.
    I’m very excited to see the first pictures.

  2. I went through two copies of the SMC-M 50/1.4 and even had one CLA’d before deciding that, for the cost and size/weight, it doesn’t perform very well in terms of wide open sharpness, compared to the SMC-M 50/1.7 which I’ve always been happy with. Bokeh may be more interesting with the 1.4 though, I’ll give you that. It seems there is maybe some sample variation with the 50/1.4’s as I never found stopping down to make it a more pleasant lens. And yes, one of mine had some mechanical problems.

    I’m a big fan of the SMC 50/1.2 and would have loved to see it included in your study. This lens is noticeably sharper at wide apertures and even when stopped down. It’s size and weight are justified to me and I happen to think it fits on a K1000 size body very well, though it’s not so hot on an M series.

    Thanks for the fun comparisons and conclusions. Always a hot topic among Pentax shooters!

    Here’s my review of the SMC 50/1.2 if interested.


  3. Good article, thanks for sharing it with us. Don’t worry about critical comments, I think most readers realize this is your subjective evaluation and their choices may be different.

  4. “Did you find this experiment helpful?”

    Well, since you asked. No, not helpful at all, really. Might be an idea next time to think the thing through from start to finish instead of jumping in and having to detail your short-comings at the end of the test.

    “Two things that jump out to me are:

    The differences in field of view between the lenses. 40mm seems quite a bit wider than 50mm, look at the powerline and sky to see how big of a difference there is. The shots are not interchangeable by any means. ”

    Did you not realise that lenses of different focal length would have different fields of view? I don’t understand why this came as a surprise to you. Have you not been taking photographs for long? If you’re an experienced photographer why didn’t you know that? If you’re not experienced then why are you bothering to “test” lenses when you don’t seem to be sure of what you’re doing?

    I don’t want to knock your effort too much but a person who has only been driving for a few weeks shouldn’t be test-driving a car for a publication. Someone with a new interest in soccer would not be found commentating on a match on Sky.

    “Wide open at f/2.8, there isn’t really much bokeh to speak of.”

    Bokeh doesn’t refer to the amount of out of focus background there is in a photograph but to the character of the out of focus areas. It’s not a matter or quantity but quality.

    “Everything is in the eye of the beholder. This test is for me to see what I like best and you to see what you like best. And guess what? We may have different opinions, which is great! Variety is the spice of life.”

    That’s a purely subjective comment and, in my subjective opinion, is an example of post modernism that serves no one well. The quality of lenses and how that is measured has been largely understood and accepted for decades. There may be one or two criteria that people might argue about – whether high resolution or high contrast is more important to the final image, for instance – but it’s most definitely not the case that “everything is in the eye of the beholder”. The important parameters can be empirically tested and measured. Putting it bluntly, Leica lenses are expensive because they are recognised as the best or, at least, right up there with the best. Crappy lenses are much cheaper because they’re crappy.

    What, in your opinion, would readers find helpful from your review of the lenses?

    1. Wilbur,

      Thank your for nailing my frustration with the article. How was he planning to test sharpness with the low-res scans (apparently he still manages to prioritize low cost over image quality in writings about image quality… even though he went out and purchased 5-6 redundant lenses) and these egregiously compressed examples? Why isn’t he giving us his conclusions instead of asking us for ours based on his terrible examples? Why not show what the lenses look like and their relative size since apparently that’s a consideration of his? And why conclude with that dismissive point of image quality and lens quality being subjective? If that’s the case, why write the article at all?

  5. Very interesting article, thank you!

    A couple of comments:

    – Unless you have a very, very unique M50/f1.4, it has 8 aperture blades, not 7.

    – 52mm was the standard filter thread for normal sized K-series lenses (my 50/f1.4, 50/f1.2 and 85/f1.8 are all 52mm). This was dropped down to 49mm for the M-series (my M28/f2, M28/f2.8, M35/f2, M50/f1.4 and M100/f2.8 are all 49mm).

    1. I was thinking the exact same thing and I was curious if anyone would notice…Maybe I shot it with the MX??? But all my notes say ME Super and I took the shots of the lenses on a different day then I actually took the photos. The 50mm/f2 is also missing from the shot. EM- Did you switch the pictures around 😉

  6. I have all of these except the 40. I agree that the 55 is really wonderful. It might be the only Pentax 50mm anybody needs. Unfortunately, the 50/1.7 doesn’t stick as far off the camera, which is especially nice on the M bodies.

    1. The 50s are bit more compact for sure, but they still can’t fit in the pocket so I bought the 40mm 🙂
      The 55mm focal length was the std “normal” focal length for a period of time before falling out of favor to the 50mm, I think it deserves a comeback!

  7. I think many of the SMC PENTAX prime lenses had 52 mm filter threads, while many of the M and A lenses had 49 mm threads. Further than that I haven’t really ventured! (It does annoy me that companies like Fuji have gratuitously many different filter thread sizes on their otherwise wonderful lenses.)

    1. I want to dig a little deeper into this idea. All my Takumars have 49mm threads. The vast majority of K-mount lenses (prime and zoom) I’ve run across are 49mm but the earliest K-mount lenses seem to be 52mm. Perhaps I need to find some early samples of the 50/1.7 and 50/1.4 to check their filter size???

      1. Don’t dig too deeply! Chris’s comment though, in the right direction is inaccurate. Pentax lenses are typically 49mm as you state. Canon and Nikon are typically 52. Only larger/faster Pentax’s like the 50/1.2 is 52mm. All there of these brands are pretty consistent with this for accessories, which makes for a nice system.

        1. If you did dig deep, or actually quite shallow, you’d find that actually Chris is correct. The early K mount Pentax lenses were typically 52mm threads changing to typically 49mm threads when the lenses were updated and took the M designation. http://kmp.pentaxians.eu/lenses/