Forgot Password
Pentax Camera Forums Home
Log in or register to remove ads.

Third-Party Pentax Lenses - Reviews and Database » Carl Zeiss Lenses » Prime Lenses
Carl Zeiss 20mm F2.8 Flektogon MC Review RSS Feed

Carl Zeiss 20mm F2.8 Flektogon MC

Reviews Views Date of last review
6 53,114 Tue June 29, 2021
Recommended By Average Price Average User Rating
100% of reviewers $145.00 8.33
Carl Zeiss 20mm F2.8 Flektogon MC

Carl Zeiss 20mm F2.8 Flektogon MC
Carl Zeiss 20mm F2.8 Flektogon MC

Focal lenght: 20mm
Aperture range: 2.8 - 22
Nr. of aperture blades: 6
Filter size: 67mm
Min. focusing distance: 0.19 m
Special feature: MC (multicoating)
Focus: manual
Mount: M42 screw mount
Mount Type:
Price History:

Add Review of Carl Zeiss 20mm F2.8 Flektogon MC
Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 1-6 of 6
Senior Member

Registered: June, 2011
Location: Gotland
Posts: 159
Lens Review Date: June 29, 2021 I can recommend this lens: Yes | Price: $300.00 | Rating: 10 

Pros: For practical purposes distortion free up to outer corners. Fine colours.
Cons: None with a lens hood.
Sharpness: 9    Aberrations: 10    Bokeh: 7    Handling: 10    Value: 10    Camera Used: K-1   

I looked for a long time for a superwide lens with easily corrected distorsion. Then I found this lens with distorsions that are neglible for practical purposes.

Carl Zeiss Jena DDR Flektogon 20mm f 2,8.

My copy was made in 1976. I bought it CLA-d from Germany (actually eastern Germany not far from Jena). By now I have used it for three months. Usually I use f/8 and ISO 100 if the avaible light permits.

Everything works very well except for the fact that "infinity" as marked is beyond infinity. The 4 meter mark works okay. For closer focus I use Live Wiev or the cameraīs focus confirm beep. I intend to fix that minor problem.

The best feature: Straight lines are rendered essentially straight. This makes composition a lot easier than the usual barrel distortion. At the very corners there is some pincushion distortion.

I did a test, photographed a tiled surface. There was a small amount of barrel distorsion in the centre and a correspondligly small pincusion distorsion at the edges. These even out and for practical purposes the lensīs output can be used as-is.

With modern lenses, I start out with minus 0,7 exposure correcton, with this one 1,0.

General photo quality is astonishingly good for a 1976 superwide lens. In great light you can get great pictures. The lack of distorsion makes the superwide field of view look quite normal.

In some situations a strong light source outside of the field of view gave artifacts. I added a lens hood. It helped a lot and also improved general photo quality. With that hood the lens is very, very good.
New Member

Registered: December, 2016
Location: The Hague
Posts: 2
Lens Review Date: July 24, 2019 I can recommend this lens: Yes | Price: $150.00 | Rating: 8 

Pros: Punchy color rendering and contrasty character
Cons: Sharp only at small aperture. Prone to flare.
Sharpness: 7    Aberrations: 9    Bokeh: 3    Handling: 9    Value: 8    Camera Used: Fujifilm X-T1   

I use only vintage analog lenses, and this is one of them I've been using for several years. It is the Zebra version that fits a 77mm thread that I stepped-up to 86mm to avoid vignetting when using on a shift adapter.

In FF simulation, using a ZhongYi Turbo II focal reducer booster on an APS-C camera, the edges show soft all the way up to f/22. Center area is sharp from f/8.

In APS-C modus, using a Fotodiox Shift adapter, the edges show soft up to f/11-f/16, which is very disappointing. Center area is sharpest at f/11. Corners show sharp at f/22 but then the center softens. The sweet point is f/11.

Rendering of color and contrast is really punchy and warm.

Compared some Flekt basics to my Asahi Pentax Takumar 17/4:

1) Flekt needs f/11-f/16 to match Tak f/8 in sharpness
2) Flekt needs about 25% longer exposure than Tak at same f stop
3) Flekt is rectilinear, but Tak is fisheye

Compared some Flekt basics to my Zenitar 16/2.8:

1) Flekt needs f/16 to match Zen f/6.3 in sharpness
2) Flekt needs about 50% longer exposure than Zen at same f stop
3) Flekt is rectilinear, but Zen is very fisheye

My Flekt got completely overhauled and is 100% clear and clean. I tried to sell my Flekt on ebay, but to no avail. So I decided to keep it on the Fotodiox Shift adapter as a cheap alternative to the expensive Canon FD 35 TS. No comparison of course, as that Canon is much sharper than the Flekt.

Anyway, throughout the past years I've been shooting with this lens as a rectilinear wide shift lens, overall nothing but good results, many of them posted on Nat Geo YourShot. Except for a slight post sharpener nothing else needs be processed.

It is a slow lens, f/4, (im)practical sweet spot of f/16, good for bright daytime outdoors only, yet at somewhat higher ISO (I use 800). I love the 100% manual handling, as I have always been used to ever in the analog era I grew up.

I am still amazed by its architecture, such as a huge front element and a tiny iris. But the aperture ring is a bit flimsy which does not match the sturdiness of the rest of the milspec barrel. Same kinda weirdness with the other zebra Flekt lenses and the Arsat 30 P6 Fisheye. I guess the engineers that time got heavily underpaid.

The zebra barrel looks sexy, and matches my silver edition camera so nicely. I love its heavy weight, both for camera stability and body fitness :-)

I am using it nowadays on a Fotodiox Shift adapter on APS-C mirrorless and so I basically have a very nice medium wide shift lens. I just cannot afford the very much wanted Canon FD 35 TS, so heck I have to make do with this combi. I'm not interested in the Samyang TS because of the moustache distortion that I do not like. Nether do I consider the Hartblei 35 TS due to the weird 20 deg rotation notches. If I want more fisheye style then I use my Zenitar 17.

This Flekt is somewhat unforgiving in terms of focusing. The slightest deviation from precise focus gets rewarded with softness. Even using a focus assistant, focusing remains a challenge every time again. Fortunately the focus ring has a decent approx 300 degrees travel. At f/16 I get the highest sharpness.

Registered: January, 2017
Posts: 413

4 users found this helpful
Lens Review Date: January 22, 2019 I can recommend this lens: Yes | Price: None indicated | Rating: 10 

Pros: accurate colors, wide, small, mechanically superb, possible to mount filters 67mm, easily correctable distrotion
Cons: not sharp wide open, has to be stopped down to be relatively sharp in corners, not that flare resistant despite being multi-coated
Sharpness: 10    Aberrations: 9    Bokeh: 9    Handling: 10    Value: 8    Camera Used: Pentax K-1   

I had actually been gifted this lens for 20$. I don't know what the reason was. It had fungus behind front glass and glass was not in pristine condition to say frankly. From the outside it was intact. Besides not having a hood and lens caps it was pretty ok. The wide focal length that I wanted for some time for K-1 but just could not find a suitable lens.

It is M42 and by using standard M42 to K-mount adapters you will not be able to fix it in a position on camera as it will always rotate a little bit while focusing. Some M42 lenses are totally fine as when they are screwed into the camera body they will firmly press onto the mount at the body and stay firm. I noticed issues with Pentacon lenses and this Carl Zeiss Jena is not much different. So, I had to drill a small hole at the mount of this lens to accommodate locking pin from the camera body when the lens is fully screwed in. No more wobbling if this is done precisely which I did. The lens becomes locked onto the body like any other Pentax K-mount lens. That works great now.

Initially lens had to be cleaned from fungus which now makes it fungus free, for how long I don't know. It was not that serious as the front glass element can be removed easily. Focus adjustment for this lens has to be done when front lens group is removed in which case you can't use live view to adjust focus. Using live view is possible on some Pentax lenses as the focus ring can be rotated to required position by removing couple of screws beneath front name plate while lens is on the camera and focusing to infinity objects. Mine is still not adjusted in a way I want, i.e. so that infinity mark on the lens corresponds to real infinity. This is extremely hard to get with this lens. So probably you will have to live with some other number as infinity on the infinity mark scale. Infinity can be identified during maximum magnification in live view.

The lens gives accurate colors. It is pretty sharp in the center when stopped down to f8 and gets sharper in the corners when stopped to f11 and f16. That is good for landscape applications. At f2.8 it is not usable wide open for objects further than a meter, from the lens but at f2.8 is very good for close-up things. It can get as close as 19 centimeters as per specification but I've see it's less than 10 centimeters. This is great for close-up shots of flowers and similar objects in which case it gives pretty good bokeh.

This lens is a real chromatic aberration magnet. From purple fringing to others even when stopped down. Especially it doesn't like shooting to the harsh sun. Terrible flares. But shooting sunsets is not a problems as the sun gets weaker. Someone shooting Pentax glass is easily spoiled and when trying another brand you see how good Pentax is when handling flares. I have to admit my crew in lens hood still did not arrive though.

Distortions exist, but they can be corrected with minimal loss of quality and pixels. There is Photoshop lens profile that works. Also, chromatic aberrations are successfully removed by one click in PS Camera Raw. So that is fine.

On eBay this lens reaches very high prices. Really I don't know why. Modern lenses are sharper and free of silly chromatic aberrations. Guess this is due to Zeiss name on it, it's small size, mechanical quality, buttery smooth focusing ring, beautify craftsmanship of the past, and due to the fact that wide lenses are rare to some extent compared to other focal lengths.

I would recommend this lens if you can get it for good price and are ready to modify it if you're on Pentax. You will have to drill a hole to lock it otherwise it will rotate. I'd suggest some modern glass in case you're ready to pay several hundred dollars for an old lens. The problem is that for full frame Pentax there is no modern wide angle primes. You're left with amazingly big 15-30mm f2.8 whereas slower zooms are not available except hard to find legacy Sigmas and Tamrons. Also, there are Pentax equivalents in 20mm who fetch similar or if not greater prices on eBay but could be better from this Zeiss as well. I guess buying these lenses directly on eBay is not the best option as the prices get inflated by reselling these items by people who actually not use the glass. So, some auctions elsewhere are preferred.

EDIT: After using this lens for one year already, I discovered that the rear elements are not pretty clear as there were some nudges from aperture blades oil. After opening this lens and cleaning the oil, I have also cleaned the elements on the rear from something that looked like fungus. Not all is clear. Since I have put the lens together and re-tightened everything, I found that amazing this lens became sharp at f2.8 without veil or softening. Also, it lost chromatic aberrations. I concluded that perhaps besides oily and fungus infected glass which caused soft images, chromatic aberrations must have been caused by elements not being put together tightly enough. So, in the end I must adjust the score again and award higher mark to this lens - 9!

EDIT No.2: After using this lens to take photos of flowers and insects, I must say that this lens is beautiful flower lens. It never disappoints in a nice day at f2.8. So I must change my mark of it to 10.

Junior Member

Registered: January, 2016
Location: Warsaw
Posts: 32
Lens Review Date: April 30, 2016 I can recommend this lens: Yes | Price: None indicated | Rating: 8 

Pros: 20mm, colors.
Cons: Price !!
Sharpness: 8    Aberrations: 9    Bokeh: 7    Handling: 10    Value: 9    Camera Used: K-3   

One of over-priced lenses in digital era. Very, very good with film.
On analog :
In sharpness this lens beat a lots ultra wide players.
In colors - Zeiss - Who using a Zeiss they know about I think.
But on digital -
Sharpness less dramatically - You must stopping this @f/8.
Contrast - big problem (?)

Generally good lens and this is all - legend of this lens ... only on film !
In Poland this is lens have a legend comparable with Holy Grail in this situation proce is too big for real value.
Senior Member

Registered: October, 2008
Location: Great Plain, Hungary
Posts: 192
Lens Review Date: April 3, 2010 I can recommend this lens: Yes | Price: $90.00 | Rating: 7 

Pros: Good overall performance
Cons: Overpriced, built quality, overestimated

This is a nice vintage lens with above average performance as we tested it with a friend in a lab. Although if you are not a hardcore collector and intend to use it other than a display piece avoid paying 250-300 GBP (prices are rising) for you can find better and more convenient alternative around for the same price or a bit more.

Picture quality is acceptable in the centre but a bit soft on the edges. The biggest weakness of the lens is the built quality. Aperture tends to become sticky so be careful if you decide to buy one.

I recommend this lens but only if you can get it at a reasonable price, let's say up to 100-150 GBP depending on condition. Otherwise avoid it as it is a waste of money for its inconvenient dated design.
New Member

Registered: August, 2009
Location: Hanoi
Posts: 4
Lens Review Date: December 3, 2009 I can recommend this lens: Yes | Price: $40.00 | Rating: 7 

Pros: color, bokeh, contrast, CA control, low distortion
Cons: sharpness, slow

Some sample images:

Add Review of Carl Zeiss 20mm F2.8 Flektogon MC

All times are GMT -7. The time now is 07:16 AM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]