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I’ve been looking for a 28mm lens to complement my Contax 35-70mm f3.5 zoom lens for a while now. I imagined someday having a nice set for my A7 with the Contax Distagon 28mm f2.8, 35-70mm, and 85mm f2.8 Sonnar.

Earlier this spring I borrowed a copy of the Contax 28mm f2.8 from a friend. I was immediately in love with it- the amazing Zeiss contrast, color, and “pop.” All three together yield a look that is unique. I decided I had to have one too.

Contax 28mm f2.8 @ f8
Contax Distagon 28mm f2.8 test shot at f8. The center resolution of this lens is incredible, color moire artifacts showing that there’s more than enough resolution for 24MP.

The problem came when the only copies available were around $400. Not a bad price for a great lens like that, but more than I wanted to spend for a lens that wouldn’t see much use at work.

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Non-Revenue photography! Contax Distagon 28mm f2.8. The “pop” effect from this lens is really great, subjects separate from backgrounds very well.

So while my wife watched Real Housewives and Dance Moms one evening I set out to find a deal on the Contax and revisit the test shots I had made with the borrowed lens.

Armenoid
Crop from a 9 frame panorama with the Contax Distagon 28mm f2.8

After failing to find a deal for the Contax I started reading a lengthy forum post comparing 28mm lenses. One of the contenders was the Pentax K 28mm f3.5. A few posters claimed that it was as sharp as the Contax, all the way to the corners!

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f5.6 with good sharpness across the frame

My criteria for a good 28mm is all about how it performs with landscapes and wide shots, meaning technical performance at or near infinity. Its not a focal length I really like to use for expressive images, and certainly if I wanted an interesting 28mm I’d head right for the Distagon f2.0. But the idea of a <$250 lens that will make impressively detailed 36″ prints was pretty exciting.

Clicking over to KEH.com, there was a copy in mint condition for $140. Two business days later the little guy arrives fresh from Georgia. Excellent build quality, literally factory condition….

#TKTK Picture of the lens on A7

BUT THE FOCUS TURNS TO THE LEFT!!!

#TKTK Picture of focus marks

Immediately the bar for this lens not to get returned was raised two-fold. Working with lenses that turn this way is tough, the muscle memory to turn right for infinity is so strong its nearly impossible to work intuitively with this setup.

Now, I planned to use this lens at f8 and near infinity most of the time, which means not much fiddling with focus. I mounted it up and took it out with me for errands around the city.

Pentax K 28mm f3.5 lens test. Construction workers digging a trench in a city street.
Corner performance isn’t hugely important when you’re working with 3d planes, but the effect has a big visual impact when used well.

Now, does it deliver when you set it to f8 and focus it well? Yes. Sharp as you could want it, all the way to the last pixel in the corners. It feels like its optimized for different detail frequencies than the Zeiss is, so while it is just as sharp the effect is different.

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Great sharpness across the frame. f8 with focus on the buildings.
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Looking up at the Federal Reserve building in Lower Manhattan. Pentax 28mm K 28mm F3.5 @ f8
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APS-C Crop mode. f8

There does seem to be a tiny amount of field curvature, so to get that perfect corner you need to zoom in and adjust the focus slightly for it, but its never enough adjustment to defocus the center.

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Crop overlay of corner pixels. Not as sharp as the center, but very acceptable. Shot at f8.

There is some chromatic aberration at f3.5 and f4. Less with f5.6 and almost none with f8, but it always disappears completely when you enable CA correction in Lightroom. I did find that you need to be careful and not default to using it “on” since it actually added CA to some images that weren’t showing it.

2 frame animation showing chromatic abreaction correction on and off for the pentax-k 28mm f3.5 at f8
Animation showing CA correction turned on to remove small amount of chromatic aberration at f8.

 

Any distortion is impossible to spot. I didn’t correct any of these images for it. Vignetting is there at f4, and is almost gone at f8. If you need a perfect gradient I found that +20/50 correction in LightroomCC worked for f8.

Pentax K 28mm f3.5 lens test. United Nations Buildings and flags.
f8 with no vignetting correction

At the minimum focus distance the center 80% of the image was sharp, I found the edges didn’t hold up so well. This is understandable since its not a modern floating design. If I am going to get wide and close, I’m going to get the Nikkor 20mm f3.5 out and get crazy for real.

Chamomile Flowers
MFD at f8
Pentax K 28mm f3.5 lens test. Pile of Red Beets.
f5.6

The bokeh is good. Not distracting even though you will see your out of focus highlights as pentagons starting at f4.

Pentax K 28mm f3.5 lens test. Jars of pickled vegetables at a farmer's market.
f8 near MFD
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Crop showing the pentagon iris shape in out of focus highlights at f8.

The 5 bladed iris is one of those things I wish was some mad-scientist lens tech could fix for me. The dream would be transplanting the nicer 8-blade iris from a donor 50/1.4 lens, but I doubt I’ll be using it closer than 10′ very often.

Pentax K 28mm f3.5 lens test. Fire call box on street corner.
f3.5 wide open. Notice the vignetting effect.
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Crop showing bokeh wide open at f3.5

All told I love the value proposition of this lens: Mint for $140 and it delivers a pleasing image and all the resolution you need for big prints. A quick check on Ebay and it sold for as little as $50 recently. At that price point it means that I’m much more likely to bring this lens out to the playground, shove it in my bag going out for errands, or just loan to a friend for their vacation.

In the end, I can’t get over the Contax. Its rendering, focus turn, and it can be readily converted to EF mount- making it a “revenue-generating” piece of kit for work. Look for that review soon!