There's debate about different 50mm prime options for Pentax K mount. I've participated in some, pitting lenses like the Pentax M 50mm f1.4 vs. the f1.7. Or how I've considered my "Sears" Chinon 50mm f1.7 (more on the name later) to be more artistic due to softness vs. other options I have. Also I see the DA 50mm f1.8 mentioned as not being full frame compatible. I thought I would do a fast comparison in my dining room to show how these lenses perform relative to each other in that setting. This review is not very comprehensive; there's a single scene being used as a test subject. There's no extremely bright lights for testing flair resistance. ISO automation and ranging was used to allow for stopping down the lens and reaching proper exposure. So take this with some grains of salt and see what you think. Maybe I'll add to this in the future to show more aspects of these lenses (assuming I still have them all, a few are for sale).
The lenses under test;
From left to right, there's a Sears-branded 50mm f1.7 that I am fairly certain was made by Chinon. Next to it is a Chinon 50mm f1.9. Next is a Pentax M 50mm f1.4. Then a Pentax M 50mm f1.7. Second to last is a Pentax F 50mm f1.7. Finally is a Pentax DA 50mm f1.8. All of these lenses are focused to infinity and are sitting in Asahi Pentax rear caps. They're all similarly sized; the DA 50, M 50 f1.4, and Sears/Chinon 50 f1.7 are the largest. The DA 50 is internally focusing so it doesn't get larger when focused away from infinity. It's also the lightest although that Chinon 50 f1.9 is pretty light as well. The Sears/Chinon 50 f1.7 is a bit loose feeling at the aperture ring and sticky at the focusing ring but the optics appear clean.
Here's the general setup for testing;
Same table, same "warm" room, etc etc from my 28mm Comparo. Camera is my Nikon Z5, a 24megapixel full frame mirrorless camera, with a PK to Z lens mount adapter that can control the stop down linkage to control lenses that lack aperture rings. White balance was set to 5000k for all shots. Shutter speed was 1/50th for all shots; automatic ISO was allowed for finding correct exposure and none of these images ran to what I would think is beyond allowable for helping show off the quality of each lens (2200 is the highest I remember seeing). Processing was limited to resizing and cropping; RAW image files were created in-camera, Adobe products used for resize, crop, and saving. All images were resized to fit the limits provided by this forum.
This is not a great test for color fringing on highlights so I'm not commenting on that aspect specifically.
I'll explain more after the first sample images. I started with my M 50 f1.7, shot at f1.7;
Focus peeking was used to quickly find focus with the hat logo being the target. I wanted something a bit off center to evaluate more of the image circle than just on-center subjects. The logo is right at 36", about 1 meter, from the camera.
Here's a crop of the hat; all of these crops are at about 110%, or just a bit larger than full size.
Next, I shot the M 50 f1.7 at f2.8.
Finally I took a shot at f5.6.
Thoughts on the M 50 f1.7: This lens was a little more soft than I was expecting to see wide open. Otherwise I think it's pretty good here, would be great for portrait work, and I'm considering it to be the benchmark for this test.
Next I tested the Sears/Chinon 50 f1.7.
At f2.8;
And at f5.6;
Thoughts on the Sears/Chinon 50 f1.7: Very soft wide open but sharpens up decently at f2.8 and things are great at 5.6. Very similar colors to the M 50 f1.7.
Next up was the DA 50 f1.8. Here's the lens wide open;
Here's the lens with the camera giving very similar ISO numbers as it did with the other lenses set to f2.8 (this might be very slightly more closed than the others but it's small if at all)
Here's the DA 50 at something similar to f5.6;
Thoughts on the DA 50 f1.8: Not as much fun to manually focus as the manual focus only lenses in this test with a short focus ring throw and not great feeling at the focus ring. Probably the sharpest lens here; I don't think I got focus exactly perfect when the lens was wide open which doesn't help things. I do notice just a bit less wide-open glow with this lens, however. This isn't the best test for vignetting but to my eyes what vignetting exists here is minimal and the lens is perfectly usable on full frame. For a K-1 or AF film Pentax shooter this might be a great way to get a light, cheap 50 with good wide-open sharpness.
Next was my Chinon 50mm f1.9;
At f2.8;
And at f5.6;
Thoughts on the Chinon 50mm f1.9: Nothing interesting here. Not very sharp wide open but kind of flat in rendering perhaps. Nice sharpness stopped down. Does nothing wrong and should be very cheap to acquire, is small and my copy feels very good to use.
Next was my F 50 f1.7;
At f2.8;
And at f5.6;
Thoughts on the F 50 f1.7: Overall great performance. Maybe a tiny bit less sharp wide open vs. the DA 50 f1.8 but overall a pretty competent set of results.
Finally I tested the M 50 f1.4. I took a test shot at f2.0 to show what this lens does one stop down from wide open. First shots here are at f1.4;
At f2.0;
At f2.8;
And at f5.6;
Thoughts on the M 50 f1.4: Very competitive results in this test. Not bad resolving power wide open and by f2.8 it's doing great things in this test. Doesn't handles sources of light well in the frame when shooting at or near wide open.
Final Thoughts: I'm going to share the most important things I learned about my two Pentax M series 50's that were tested today: The Pentax M 50 f1.4 is just as sharp overall as the M 50 f1.7 when capturing objects which are not sources of light when shooting both wide open. And the f1.4 lens is definitely worse at handling in-frame sources of light (in this case, Christmas lights on a string) in-frame wide open where the M 50 f1.7 doesn't have that veiling flair surrounding the light source that the M 50 f1.4 does.
The Chinon 50's seem like decent lenses and if I shot portraits I would really like to try the f1.7 optic against the other lenses to see if I would prefer its rendering and softness at wide apertures. This is one of a few lenses I consider great for artistic shots and these tests confirm that use. I think the f1.9 is fine; nothing to get excited about but a potential great value purchase.
The F 50 seems quite competent but it's hard for me to imagine a use case for it where the DA 50 f1.8 doesn't make just as much sense for less cost. Both are not much fun to focus manually.
The DA is probably the sharpest lens in this test but is the least nice to use via adapter onto a non-K-mount camera. If I ever got my Super Program into use it would be fun to test on film.
I hope this was useful. Outdoor tests, tests to show how they act at minimum focusing distance, or how they render people on this same camera would all be useful and maybe will take place in the future.
Last edited by pres589; 10-12-2024 at 01:01 PM.
