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Cosina 20mm f3.8 MC

Reviews Views Date of last review
3 32,301 Sun June 21, 2020
Recommended By Average Price Average User Rating
67% of reviewers $84.17 7.50
Cosina 20mm f3.8 MC

Cosina 20mm f3.8 MC
Cosina 20mm f3.8 MC
Cosina 20mm f3.8 MC

Auto aperture, manual focus
Mount Type:
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New Member

Registered: June, 2018
Posts: 13
Lens Review Date: June 21, 2020 I can recommend this lens: No | Price: $55.00 | Rating: 6 

Pros: hey, it's a 20mm!
Cons: mediocre sharpness and contrast on low apertures, distortion, not amazing against bright light, poor QC on my copy
Sharpness: 4    Aberrations: 7    Bokeh: 7    Handling: 9    Value: 6    Camera Used: K1000   

I am having some mixed feelings about this lens. It has an amazing field of view but is not that amazing in regard to the image quality. I bought it for my K1000 because I wanted to do some photography with an ultra-wide lens and I was too cheap to buy the Pentax-M 20mm. This lens is apparently the same lens as Vivitar 19mm f3.8, so I also recommend to read the reviews of the Vivitar lens.

Built and handling
The lens handles very well. The focus is very smooth and the aperture ring is very easy (maybe even too easy) to turn. It clicks every stop (not half stop as in many pentax-m lenses). There seems to be poor quality control. The feet/meter scale on my copy is not properly calibrated which is a bit annoying but to be honest it has no influence on the pictures. What does have some influence on the pictures is some likely misalignment of the optics inside as one side of the picture is softer than the other. However, that concerns less than 5% of the frame so it is also not too critical.

Taking pictures
Fully open the lens gives a soft and low contrast look with very soft sides of the picture. In general if you don't like a dreamy look you should stop it down. On film, the best results are usually obtained at f11 of f16. At these apertures the center of the frame is decently sharp, but the sides of the frame remain a bit mushy. Distortion is pronounced but unless you are photographing architecture it should not be a problem. Bokeh does not seem to be bad. If you shoot against the sun be prepared for flares and drop of contrast. I mostly shot B&W so I cannot say much about chromatic aberration. Vignetting is visible on film at f3.8 but gets less of an issue with stopping down.

In general this is a funky lens and if you can get it cheap you can have a lot of fun with this "poor man's" ultra-wide angle lens on a 35mm camera. You just need to keep it stopped down to get a decent contrast. The corners and the edges on the long axis of the frame will always leave something to desire though. Thus, if you want to do some large prints with plenty of detail you should probably look for a different lens. For snapshots and lo-fi photography it is fine. I am sure, however, that a skilled photographer can make a good use of this lens.

Here are two example pictures:

New Member

Registered: September, 2011
Posts: 2
Lens Review Date: December 11, 2016 I can recommend this lens: Yes | Price: $47.50 | Rating: N/A 


Just bought this lens on 'marktplaats' local dutch ebay alike site. Wanted a fixed wide angle lens to play with. Will update review when I have received this lens.
New Member

Registered: March, 2012
Posts: 1

4 users found this helpful
Lens Review Date: October 1, 2012 I can recommend this lens: Yes | Price: $150.00 | Rating: 9 

Pros: light, small, easy used, price
Cons: no auto, shapness
Sharpness: 9    Aberrations: 9    Bokeh: 9    Handling: 9    Value: 9   

I have one 20 3.8A, the picture address is
I use this lens fixed focus, take a lot of pictures.

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