Minolta MD 28mm f/2, Pentax SMC 28mm f/3.5, Contax Distagon 28mm f/2.8. What are the differences? – Four Billion Years

The 28mm focal length is versatile, but not easy to use. Street photographers like it because of how much they can fit into it, but in order to be effective it is necessary to get very close to the subject. The attraction for landscape photography is that a 28mm scene, if properly composed, looks natural, in the sense of appearing to be what the eye can grasp, yet being wider than the human field of view. Although walking and exploring an urban landscape with a small and sharp 28mm lens can be a joy, some are troubled by the distortion that even the best of these lenses have, and by the stretching that is an unavoidable consequence of geometry. I must confess that I spent many years thinking that any lens between 24 and 50mm was a waste of time, but I am finally learning to appreciate focal lengths in the 28-35mm range, and also learning to work with their challenges. These challenges are, I think, greater than those posed by 18-24mm lenses, because it is a lot easier to pull-off an eye-grabbing image with an ultra wide angle lens than it is to compose a beautiful and balanced “normal” wide angle image at 28-35mm. It is also harder to get a strong focal point in a 28mm composition than in a 50mm one.

Never one to go only part of the way about anything, when the 28mm bug bit me I decided to do some homework that included buying lenses, using them for a while, selling some and keeping others. Among the excellent lenses that I did not keep were a Leica Elmarit 28mm, a Hexanon 28mm f/3.5 (7 element version), two versions of the Minolta MD 28mm f/2.8, a 28mm f/2 Rokkor MC and a 28mm f/2.8 Zuiko. The reasons why I let go each of these lenses varied, and in most cases it was chiefly to fund other purchases. All of them are excellent, and the Hexanon in particular is a true underappreciated gem. But I finally settled on three lenses that I intend to keep, again for a combination of reasons, among which are image quality and “mount rationalization” – with mirrorless cameras (I shoot only Sony A7 series) I try to switch adapters as little as possible. These are the three 28mm primes that I will be writing about here. In alphabetical order, they are: (i) a Minolta MD 28mm f/2, the very last “post-Rokkor” version; (ii) a Pentax SMC K 28mm f/3.5, pre “M”, and (iii) a Zeiss (Contax) Distagon 28mm f/2.8 MMJ. If you don’t have time to read what follows or look at the images, here is the spoiler: the results are virtually identical. In a blind test I would be hard-pressed to tell which image came from which lens, and then only if I looked very carefully.

Some general information about the how data were collected. All pictures were shot with a base 24 Mpixel Sony A7 mounted on a tripod and at ISO varying from 100 to 400. I focused manually on some sector of the image with plenty of fine detail, using image magnification and focus peaking. Images were recorded in raw format and then processed in Capture One. I did as little processing as possible: white balance correction, a bit of exposure and contrast adjustment and some sharpening, but no noise reduction whatsoever, and no local adjustments. In two cases I converted to B&W, also in Capture One. I did all of the processing always on the same “standard” image for each scene – the picture shot with the Minolta lens at f/8 – and then applied these settings to all of the versions of each scene. Thus, the processes applied to the Minolta, Pentax and Zeiss lenses (always displayed in this order, by the way) are identical, and any differences between them can be assumed to reflect differences in the lenses, in addition to small changes in illumination which will be obvious and should not affect the conclusions. Speaking of illumination, we have had a terribly rainy winter and early spring in Georgia and I eventually got tired of waiting for the “perfect” day to do the shooting, so I grabbed the first couple of dry days on which I could spare the time. Not great light, as you will see, but I think that it is enough for the purposes of this comparison. One final note: trying to get WordPress to show images with good resolution, and to do so consistently across different platforms, is almost impossible. I have therefore also made the images available on my portfolio site, hosted by Zenfolio. Go to https://www.fourbillionyears.com/clients.html and enter 28mm as Gallery id and Wideangle as password. They should look significantly and consistently better there. 

Let us begin with an image that has considerable depth of field, which may serve to compare the qualities of these three lenses as landscape tools. I chose this location at the State Botanical Garden in Athens (Georgia, USA) because there is plenty of fine detail, in the fallen leaves, bark and naked branches, and those details are spread out over at least 100 meters of depth. I focused on “infinity” using the bark of the distant trees on the right of the trail. The full images shot at f/11 first (you can click on the lightbox to get a dark background, both here and in the portfolio site):

At this scale I find it impossible to detect any significant differences in sharpness, contrast, depth of field or overall “pleasantness” among the three lenses. The one difference that is noticeable, but not great, is in color. The Pentax lens is a bit cooler, the Minolta is a bit greener (not too different from how a Leica would render), and the Zeiss a bit warmer and, perhaps, more accurate. But the differences are small and could probably be made to disappear with a bit of color editing, or simply kept, as they are part of the character of each of the lenses.

We can now look at the details in three different parts of this scene: the near field in the lower right corner at f/11 and in the lower left corner at f/16, and the path and distant trees at the top at f/11. I chose these apertures to do these comparison because they are the ones that I would use to shoot a landscape while trying to get as much of it in focus as possible. All three lenses go to f/22 but the image quality suffers noticeably, so I discarded those shots.

In the first three images, the lower right crop, if you look at the fallen branch coming towards you and the leaves at the bottom of the frame you will notice that the Pentax is sharper and that the other two lenses are about the same. I don’t see a difference, however, on the tree bark and on the moss on the bark. Looking at the lower left crop (the next three images) the Pentax and Zeiss are virtually indistinguishable and the Minolta just a bit weaker, but the difference is again small. Perhaps more importantly, I see no noticeable loss of quality in any of the three lenses between the previous images shot at f/11 and these shot at f/16. The three last images, a crop of the top center, show that the Zeiss is better at resolving the fine naked branches in the distance, especially those set against the bright sky, but there is virtually no difference among the three lenses in how they render the leaves and the bark of the trees in the middle and far distances. Now, discussing these differences amounts to pixel peeping, and is not photography. Looking at what really matters, what the image looks as whole, my conclusion is that, as landscape lenses, where what matters is good and even sharpness at small apertures, good contrast, balanced color and lack of vignetting, there are really no significant differences. 

In the next three images we see a friendly raccoon guarding a tree nut. These are crops that represent about 60% of the original images, shot at f/5.6 and using the tip of the raccoon’s nose as the focus point. We can use the raccoon’s “fur” and the tree bark to compare sharpness at what may be close to the sharpest aperture, and at the same time judge the ability of the lenses to generate a three dimensional feeling by separating a close in-focus subject from an “infinitely distant” out of focus background. As best as I can see the three lenses are comparably sharp over the in-focus area, and all three have a pleasant out of focus rendition of the distant background. The different color rendition is quite apparent, though, especially if you look at the varying  tint in the white portions of the raccoon.

There is an old tool shed next to the University of Georgia campus that has a rusted iron door with plenty of fine texture and color detail. First a picture, shot at f/8, of the top of the door together with the surrounding wall and some ivy hanging from the roof of the shed. The full frame images are followed by crops of the top of the door itself, near the center of the field of view. The color difference is again quite noticeable. In the overall image I get the impression that the Pentax lens brings out slightly more detail than the other two, or perhaps that the image that it renders has more of a sense of presence. The difference is very small, if not entirely subjective. In the crop of the top of the door, however, I cannot detect any difference.

A different composition (also shot at f/8) showing the left edge of the door, and then a crop centered on the chain. My conclusions are the same as for the previous set of photographs. 

The next series of images are close-ups of the rusted side of an abandoned railroad car in Athens (Georgia). I am always attracted to the details of old rusted surfaces and in this case I will use them to bring out some of the most substantial differences among the three lenses. All of the images are full frame, i.e., not crops.  The first three, shot at f/8, show comparable sharpness near the center, but if you look at the upper left corner the Minolta is sharper than the other two. The difference in the next three pictures, shot at f/4, is more noticeable. As I will discuss shortly, I think that this is a difference in depth of field, rather than inherent sharpness. What the f/4 shots also show is a striking difference in vignetting. There is virtually no light fall-off in the Minolta lens, whereas the Pentax, close to its maximum f/3.5 aperture, vignettes quite heavily at f/4, and the Zeiss is somewhere in between. The next two images are at f/2.8 and show that the Minolta lens holds up a more even illumination and also noticeably better sharpness across the frame than the Zeiss. The last image, from the Minolta at f/2, is similar in light fall off and sharpness to the Zeiss at f/2.8 

Complementing the photo of the stuffed raccoon, which displays out of focus rendition of distant areas with strong highlights, we can look at bokeh of more evenly illuminated backgrounds. First an old fence in the Oconee Hills Cemetery in Athens, shot at f/4 with the three lenses, at f/2.8 with the Minolta and the Zeiss, and at f/2 with the Minolta only. I would say that the out of focus area is smoother, and perhaps more pleasant, in the Minolta lens (not surprising, for a company responsible for the Rokkor 58mm f/1.2 and the 85 mm f/1.7) and “harsher” in the Pentax, with the Zeiss somewhere in between. This is still true at f/2.8, and the Minolta lens at f/2 is, well, pure Minolta.

A crop centered more or less on the second finial of the fence gives a closer look at the sharpness of the in-focus area. The three lenses are virtually indistinguishable at f/4, but the Minolta at both f/2.8 and f/2 is sharper than the Zeiss at f/2.8. The Minolta is still quite sharp wide open.

Another detail of rusted railroad cars, first the three lenses at f/5.6, then the Minolta and Zeiss at f/2.8, and finally the Minolta by itself at f/2. Along the left edge the Minolta lens is noticeably sharper than the other two. As with the earlier photo of the rusted railroad car, this edge was closest to the camera, so the difference in sharpness in both compositions may reflect wider depth of field of the Minolta lens at close distance. The differences in vignetting among the three lenses, that we saw earlier, are also well represented in these images. 

One last aspect that we can look at is the distortion of these lenses. The first three shots in the next set are uncorrected, and show comparable amounts of barrel distortion. In the last three shots I applied keystone and distortion corrections with Capture One. The results are not perfect, but they are good enough for me and very close to one another. Which means, I would claim, that any distortion that these three lenses have is not an important issue, neither in absolute nor in relative terms.

I have tried to show enough photographs to allow you to draw your own conclusions about these three 28mm primes, and I have little to add. I will only say that, if you truly want to split hairs, then the 28mm f/3.5 Pentax may be the best landscape lens of the lot, and the 28mm f/2 Minolta MD may be the best if your interests lean in the direction of close-up wide-open shots. But pixel-peeping tests like this one cannot reveal the full character of a lens, and there is where the microcontrast and color rendition of a Zeiss lens, any Zeiss lens, may make many of these differences moot. But you really cannot go wrong with any of these three lenses. The Pentax is the cheapest of the three, a bit over USD 100 for a good one, the other two are perhaps twice that much. Or, you can get a flashy new auto-everything Frankenlens for ten times as much – your choice.