Asahi Pentax Super-Takumar 55mm f1.8 and Minolta MD 50mm f1.7 lenses

A history: Lenses mentioned above are very popular 50mm fast prime kit lenses of Japanese optic manufacturers Minolta and Asahi. At one time they were regarded as the top product of the lens designing and production.

Asahi Pentax Super-Takumar 55mm f1.8 lens was released around mid-60s, when the company with its revolutionary Asahi Pentax camera was at the peak of their popularity.At that time it was allowed to use radioactive compounds (thorium oxide, for example) to get the glasses with the specific refraction of the light. This period also characterized by active development of anti-reflective coatings, the introduction of multicoatings, as well as coverage of all (internal and external) lens surfaces.

Minolta MD 50mm f1.7, is a third (the latter before autofocus lens introduced) and the most advanced generation of Minolta MD lenses, released around mid-80s. That means it made of more modern materials. In addition multicoatings technique was widely used during that period.

As showed below the optical lens scheme are very similar if not identical. Means the main performance difference between these lenses should be usage of different glasses and multicoating.

Optical schemes:

These lenses are not rare; they were manufactured in quite large numbers. At the secondary market Asahi Pentax Super-Takumar 55mm f1.8 can be bought for ~$45-85 while Minolta MD 50mm f1.7 can be bought for about half of this price ~$25-35.

Lenses, which will be compared:
Minolta MD 50mm f1.7-№ 8317617
Asahi Pentax Super-Takumar 55mm f1.8 - № 2564838

Group photo:

Parameters for comparison:

Convenience of usage and mechanical quality.

Image sharpness for a short distance (3m):

Subject picture (sharpness in the center of the frame)
DOF test (sharpness in the center of the frame)
The picture of the grid (the sharpness in the center and edge of the frame)

Image sharpness in the center of the frame (100% crop) for a long distance (150m) with closed aperture.

Vignetting

A point source of light in the background and the background blur (bokeh).

Resistance to the flare and Chromatic aberration (CA).

Capability of macro shooting.

Convenience of usage and mechanical quality.

It is difficult to say something special about these lenses. Mechanical design - perfect, the focus ring turns smoothly, aperture blades do not stuck, even a plastic aperture ring on the Minolta MD 50mm f1.7 does not seem unnatural. So, in spite of its age, both lenses are in excellent condition.

Optics for both lenses also has perfect condition - no stains, scratches or other defects. Asahi Pentax Super-Takumar 55mm f1.8 - front lens coating is yellowish, the back - purple. Minolta MD 50mm f1.7 - both lenses coating (front and rear) is purple.

The only design drawback of a Minolta MD 50mm f1.7 is the lack of half-stop between f1.7 and f2.8. Put an intermediate value f2.0 is impossible.

Image sharpness for a short distance (3m):

Conditions: indirect sunlight, ISO100, white balance fixed (the sun), Olympus E-PL1, a tripod.
Shooting at the wide open aperture requires very careful focusing; therefore, for greater repeatability of the results I tried to use several variants of the test:

Subject picture - a fish from a distance of ~ 2.5m

DOF test - sheet with marks located at a sharp angle to the camera at a distance of 2.5m. Even if the focus had not exactly matched, you can easily compare the sharpness of the image quality. At the same time to see the size of the DOF.

Picture of fine grid (1.5m x 1.5m), too, with a distance of ~ 2.5m. This test can also determine the sharpness of the edge of the frame.

100% crop DOF test

100% crop Grid Center

First method does not reveal the winner but the depth of field test leaves no doubt - Minolta MD 50mm f1.7 definitely sharper  at the wide open aperture. Aperture f2.8 and f5.6 improve the sharpness, but still a Minolta MD 50mm f1.7 has an advantage.
Test grid confirms this conclusion.

100% crop Land Grid

Test on the grid shows that the sharpness of the frame edge does not differ much.

Image sharpness in the center of the frame (100% crop) for a long distance (150m) with closed aperture.

100% crop

This test showed no difference in sharpness between lenses in the center of the frame. However, the sharpness of the frame edge a little better for Minolta MD 50mm f1.7 (look at the window blinds).

Vignetting

The naked eye detect no vignetting in these lenses, so an option has been applied in Photoshop - (Posterize Level 5)

Photoshop

It can be seen that the vignetting on both lenses is virtually absent, even at fully open aperture.

A point source of light in the background and the background blur (bokeh)

This test showed a very similar picture for both lenses. It shows very smooth circles at the wide open aperture, passing in-to the correct form of reduced circles on the edge of the frame. Closing up to f2.8 of Asahi Pentax Super-Takumar 55mm f1.8 reveals a very funny "circular saw" shape. On real photos, I think, nobody can see it.
In general - nothing extraordinary, bokeh of both lenses is pleasant. A green highlight CA for Asahi Super-Takumar 55mm f1.8 is little confusing, but more on that in the next section.

Resistance to the flare and Chromatic aberrations.

Both lenses are resisting quite well to the flare, the strong glare was not observed.Closing the aperture to f2.8 ( Minolta MD 50mm f1.7 has no f2.0 set-up) eliminates this problem.

100% crop

O-o-o-o-ps!  The chromatic aberration for Asahi Pentax Super-Takumar 55mm f1.8 becomes to be a problematic point. It is clearly seen purple and green highlights at the f1.8, which has not seen on Minolta MD 50mm f1.7 in the same situation. At f2.8 it is less noticeable, but the phenomenon is still present.

Ability to Macro shooting

By themselves, the lenses is not "macro-lenses" - the minimum focusing distance of 45cm for both is not enough. However, when using the macro-rings (for M4 / 3) it is possible to achieve a good result.

100% crop

At the f8.0 aperture (100% crop), the result is slightly better at Asahi Pentax Super-Takumar 55mm f1.8, although, in general, nothing special.

Benchmark:

I have tried to rank the objectives by a five-point system for each of the above parameter. Evaluation of course related to the specific lens and does not purport to be absolute. Exhibiting assessment, I also had in mind I used the other 50mm lenses (you can see the list on my personal page) and tried to be objective as possible.

Conclusions:

After analyzing the results, you can come to the obvious conclusion - twice more expensive lens shows the worst results in almost all respects. There is an obvious "brand name" disease - more "popular” Asahi Pentax Super-Takumar 55mm f1.8 actually is no better than unpretentious Minolta MD 50mm f1.7. I would even say that in general at the market presents kind of "underestimation" of Minolta lenses, like second-rate. So I can recommend to those who want to have a good fast 50mm prime lens, do not chase something stunning and expensive - just try Minolta...

Minolta MD 50mm f1.7 pictures galery

Asahi Pentax Super-Takumar 55mm f1.8 pictures galery