[cyberjunkie]

Some explanations for non-German speaking members in regard to the test from 2008, to which I linked in post #28.

The test included the following lenses "name elements/groups" "I" means integrated lens-shade:
SMC-F 2.8/135 8/7 I
SMC-A 2.8/135 4/4 I
SMC-K 2.5/135 6/6 -
SMC-M 3.5/135 5/5 I
Takumar 2.5/135 [Bayonet] 4/4 I
Takumar 2.8/135 [Bayonet] 4/4 I
and as a reference:
Auto Revuenon 2.8/135 ?/? I
SMC-DA 4-5.8/55-300 @135 12/8
..........................

I've gone back to your post, and downloaded the pdf of the test, plus others concerning a few vintage Pentax lenses, plus Voigtlander ones (tested on a Nikon).
I will go through all of them
I love vintage lens, and (with all the caveats, that you mentioned, at least in part) I like to see tests that show how those lenses perform.
The thread has evolved in the meantime, crop vs. FF field of view, etc... but I feel I have to congratulate for the link you provided, and for the explanation in english (for the joy of those who know nothing about german language).
I like this kind of posts. My compliments for the interesting info you made available to the forum members. I'm sure some enthusiast will find the test very useful. It will stay as a reference for future forum members, at least until the pdf's don't get removed from the Internet.

Regarding PK Takumars, I believe they were not made by Pentax, not in the same factory where SMC Pentax and Pentax-A objectives were manufactured.
No way they had a different coating process available in the same structure.
I believe they were built by a third party (all in Taiwan?), and made to look externally as all the other Pentax lenses.
They could share mechanical components, though.
I don't think the Takumar Bayonet's were inferior to most of the 135mm's made at the time. I simply believe those lenses were not Pentax, and that there could be an equivalent with different aesthetics sold with a different brand. Who knows.
The nature of the test (performed on crop format) allows the tested optics to give their best. Only the center of the field is examined.
As I'm currently shooting 99% of the times with a full frame (K-1), I'd be curious to know how the same lenses rated outside of the APS-C frame.
I guess that the number of elements has its importance. I believe that lenses made in the same period, with similar focal/aperture, designed by the same team, but with a more complex optical layout, should provide a better level of performance. Other way there would have been no interest in making them in the first place. If you can do well with only four elements, why go for six?
I believe the higher level of correction provided by a more complex design should show in particular at the borders of the image.
The center was already good enough with a classic tele design of just four elements. Especially at f/3.5.
I expect that the difference between the various optics would show more on FF, with five or six elements ones having an edge over the others.
Of course it's not only about elements number. I'm taking special glasses out of the equation... but AFAIK even in Pentax-A times no short teles used such glasses.
All that to say that it would have been nice to check FF performance... not their fault, of course the K-1 was far to come!

---

Last edited by cyberjunkie; 09-03-2018 at 11:34 AM.

[RKKS08]

A 50mm lens is still going to render like a 50mm lens on a crop sensor. You don't get a 75mm lens, just a smaller version of a 50mm image

I understand the final pictures you will be viewing on monitor (or printed) will be of equal size.
With the greater expansion from the crop sensor also the circle of confusion will change.
And thus the definition of what's inside DOF. I am not sure this is covered by your explanations.

As I see it, you won't get "just a smaller version".
If the 50mm/crop sensor picture looks different from the 75mm/FF it will rather be caused by the chacteristics of the lenses (bokeh!) than by focus length.

[RKKS08]

Regarding PK Takumars, I believe they were not made by Pentax, not in the same factory where SMC Pentax and Pentax-A objectives were manufactured.

My Takumar Bayonet 2.8/135 says "Asahi Opt. Co. Japan".
Some other lenses say just "Japan", but there is "Pentax" on the front ring.
My 2x TC (no front ring) says "Pentax Japan".

I know there are Takumar Bayonet lenses which say "Taiwan". But of course I don't know whether this means "designed in", "made in" or "assembled in".

[UncleVanya]

Back when my father worked for them - there was no indication the lenses were not made by pentax. SMC was a multiple step process. These lenses were just not coated multiple times. Coated - yes, not coated as many times with the SMC secret sauce.

[SunnyG.]

Ok this is going to be hard to prove from my own work, but I will give it a try imperfect as the comparison is going to be. All shots are of my friend Jesse. Comparison is with the Canon FL 55mm 1.2 which is generally agreed to be a good portrait lens on full frame and the FA77 which everyone agrees is a good portrait lens on APS-C or full frame.


First shot K5iis Canon FL 55mm 1.2 I am guessing this is either 1.2 or 1.4 simply because the ISO is 100 and the shutter speed is 1/40 indoors with some natural light and overhead illumination.




I like the photo well enough, but the facial lines are stronger than what I'd like in a portrait.

Second shot K5iis FA77 f2.5 ISO 100 1/125 mostly diffused natural light with some overhead. Even closed down more than the Canon, the facial lines are less pronounced.



Third from a headscarf series I did with near ideal natural light. FA77 f2.8 ISO 100 1/100




This of course proves nothing. I even like the first photo although Jesse did not because it highlighted facial lines. But objectively, the longer lens, even stopped down a bit, gives a more classic portrait look. If you are going for character and grit, then its true that a the shorter focal length will work fine and may even be preferable. But that's not typically why someone buys a portrait lens, which was the OP's goal.

Lovely pictures!