[JoelRussell]

I have an SMC-M 28mm 3.5 that I use on my Sony a7. It is one of my favorite lenses. I wanted the K version, but could not find one in good condition...at a reasonable price. I hear that the K version is better than the M version. Do any of you have experience with using both, and comparing image quality? I can not believe that the K could be that much better that the M.

[stevebrot]

I don't have either, but can say that the designs are different:

M 28/3.5 : 6 elements in 6 groups




K 28/3.5 : 8 elements in 7 groups




Steve

(...does own S-M-C 28/3.5, reputably the same optics as the K 28/3.5...nice lens...)

[jslifoaw]

I have both. The K version is definitely better though the M version is no slouch especially stopped down (and better than the F2.8 versions). The K version has very good across the frame performance at the wider apertures by comparison.

It's a bit bigger - probably about 1.5x deeper and heavier and with a 52mm filter instead of 49mm.

[7.62lew]

I have an SMC-M 28mm 3.5 that I use on my Sony a7. It is one of my favorite lenses. I wanted the K version, but could not find one in good condition...at a reasonable price. I hear that the K version is better than the M version. Do any of you have experience with using both, and comparing image quality? I can not believe that the K could be that much better that the M.

I had both although I did give the m version to my daughter. The K version is better in my opinion. Colors are different and sharp to edges from wide open. It is bigger and heavier. I have used it only on crop sensor Pentax.

You can find the K version for under $100 if you are diligent and patient. But you have to hit it just right. For me when it gets north of $150 I would probably spend my money towards a DA 35 Macro (which I also have). Another option would be K version 35mm 3.5 or Super Takumar 35mm 3.5. Not as wide but very close in performance. I have the super takumar and compared side to side, for my copies, the K28 has the edge. BUT you can get some stupid cheap deals on the Takumar...I paid less than $30 for mine.

If you get a K28 in good shape you should not have trouble re-selling. Put up a wanted ad and what you want to pay in the marketplace. You may get lucky...

This is a link to some photos with the K28 on my flickr page.

Pentax SMC 28mm 1:3.5/28 K Series Lens | Flickr

[pentaxus]

I found the K lens to be amazing. Sharp with little lens flare. I even had to use it for copy work and was amazed at the straight lines (not correctable in film days).

[pschlute]

I do have both lenses but would never bother to do a test.

Suffice to say both are very good.
.
This is the K version, as noted it is a different optical design to the M version

[Gene D]

I have an SMC-M 28mm 3.5 that I use on my Sony a7. It is one of my favorite lenses. I wanted the K version, but could not find one in good condition...at a reasonable price. I hear that the K version is better than the M version. Do any of you have experience with using both, and comparing image quality? I can not believe that the K could be that much better that the M.

I can only vouch for the K lens as I was recently fortunate enough to acquire one in near-mint condition. I have been using it on my KP. It's an amazing lens, far exceeding my expectations. Using it primarily for landscape, my biggest surprise is the rendering of the color and the sharpness, in addition the build quality. I find I do mostly minimal adjustments in post. The color is very deep, rich and contrast great. Paid just under $100 for it but did look for a while as there are typically some on eBay in the $150 range. Reviews here show it evaluated as better than the M but have not used one. At $100., the price difference is only about $30 or so more for the K. My net is that in the $100-130 range it's a fantastic price for the quality you get at 28mm manual.

[Ronald Oakes]

Better? That's a very subjective descision based on what one considers better and for what use and on what platform.
I have both and either is quite capable !
However....the 28mm 3.5 is much sharper than the M version once stopped down.
The K 28 3.5 was only made for a short period of time compared to the M version, hence it's somewhat Rare and demands a higher price.

[Thagomizer]

I do have both lenses but would never bother to do a test.

Suffice to say both are very good.
.
This is the K version, as noted it is a different optical design to the M version

A fine shot of a lovely looking subject!

[Jonathan Mac]

I've used both, including several copies of the M. The K is bigger and heavier but produces nicer images. The pictures from the M are rather dull whereas those from the K are more vibrant and look "more real". That's the best way I can think of to describe it, perhaps it's a matter of contrast or micro-contrast, I don't know. In terms of sharpness there's no real difference, both perform very well even wide open.

[jopenmx]

I never tested the M 28 f/3,5 , but all the opinions and tests ( Takinami, etc ) seems agree that the K version is superior in almost everything , sharpness edge to edge, contrast, etc . I have the K 28 f/3,5 since more than 20 years with its original hood , and have used with film bodies like Z-1p, LX, MX and KX and then with all my DSLR K 10D, K-3 and K-1 . This lens is amazing specially for waterfalls and beach sea scapes because the rich tones blue and green. The optical ( 8 elements , 7 groups ) is not the same than the Takumar and S-M-C Takumar 28 f/3,5 , and the design was not a cheap one. However, It had a very short production life ( 2 years ).
Afterwards , I have got also K 28 f/2 ( which is amazing , of course ) and A 28 f/2 as well as FA 31 . In spite of this, I would say that K 28 f/3,5 it´s still one of my 5 favourite lenses and will never sell it.

[7.62lew]

One is for sale in the marketplace...not mine!

MF: Pentax 28mm,Pentax 55mm,Pentax-M 50mm f1.4,Pentax-M 100 Macro,Pentax-A 50mm Macro - PentaxForums.com

[JoelRussell]

I just wanted to thank you all for the insightful feedback to my question regarding these two lenses. Much appreciated!