Zenitar 16mm f/2.8 Fisheye

It is very difficult to design a lens that covers a large field of view (FOV) without distorting the captured image. As an example, the smc PENTAX-A 1:3.5 15mm offers a 111 degree FOV (examples). When going much further than that, distorsion is unavoidable. In some situations the distorsion is an acceptable price for a large FOV, and today it can even be reduced or removed with image processing software. Consequently, there is a market for lenses with an extreme FOV – up to 180 degrees – usually called fisheye lenses. Depending on their design and focal length these fall into either of two cathegories:
a. Full frame fisheye lenses capture a hemispherical image across the diagonal of the 35 mm frame. These lenses range in focal length from 14-16 mm.
b. Circular image (hemispherical) fisheye lenses capture a full 180 degrees within the narrow height of the 35 mm film frame. The lenses in this class have effective focal lengths ranging from 6 to 8 mm.

Henrietta and Tamae guard my Zenitar MC 16mm f/2.8 Fisheye lens.

The advanced design of fisheye lenses with many elements and small series usually makes them rather expensive. An exception to that is the Ukrainian Zenithar that can be bought online for little more than $100. Although the quality is not always up to Western standards, many former East Block lenses take very good pictures. If you just want to experience what it is like to use a fisheye lens without emptying your bank, The Zenithar (or the even wider Peleng) is a must.
The FOV of the Zenithar is about 180 degrees diagonally on 24 mm film. On the APS-sized DSLR sensor it is correspondingly less but still impressive. One other aspect of the fisheye that it shares with all short lenses is a very large depth of field, objects close to the camera is sharp even when the lense is focused at infinity. One disadvantage of this is that it can be difficult to focus manually at close range, everything looks sharp in the view finder!

Examples

Uncropped closeup of flowers and Yoshiko with typical fisheye distortion (1/90 f/16?).

Slightly cropped closeup of sunflower with bee (1/1000 f/8?).

Ten centimeter Achiko Pinky and 190 meter Turning Torso (1/180 f/22).

Close photo of bicycle with typical bending of straight lines (click for larger image).

Unretouched crop showing the fine resolution of the Zenithar.

Don’t Panic!

I was rather surprised and a little alarmed when I noticed that my brand new fisheye lens was unsharp at infinity, in fact, I had to look at an object as close as about a yard to see something in focus. Only with a small aperture did distant objects come into reasonable focus. I guess this is the result of what some call “creative quality control at the factory.”
A kind member of the Pentax Discuss Mail List directed me to a review by Erik Tischer that described the same phenenoma, but also how the unsharpness could be corrected. I will outline the process in more detail below.
The problem was that the outer focusing ring was not correctly aligned with the internal focusing mechanism. Since the movement of the outer ring is limited by a pin that runs in a grove in the lens body, it could never travel far enough to focus on infinity. Indeed, other examples of this lens has had the opposite problem, having been focused beyond infinity. The remedy in both cases is to realign the outer ring.
Here’s how to do this. Carefully slide the rubber band on the ring down over the aperture ring. I used my nails to get a grip on the rubber, it is best to avoid tools that might damage the surface. You will find three screws under the rubber band (see image).
Set the focusing ring to infinity and unscrew all three screws as much as it takes to loosen the ring, one turn should be enough I think. Move the loose ring to feel the end stops and position it about half way between these. Tighten one or two of the screws.
Mount the lens on your camera body and focus on an obejct at infinity. Loosen the screws again and move the outer ring the infinity position. Check the focusing at different distances. The distance values at close ranges may well be incorrect after the adjustment. It may be possible to rectify this and still keep the lens sharp at infinity but I did not bother. Tighten all the screws and reapply the rubber band.

Specifications

Lens construction: 11 elements in 7 groups
Angle of view: 180° diagonally on film camera
Number of diaphragm blades: 6
Minimum aperture: f/22
Minimum focusing distance: 0.3m
Filter size: 26.5mm rear mount (four filters included)
Maximum magnification: 0.13X
Dimensions (diameter x length): 63mm x 49mm
Weight: 310g

Pentax Fisheye Zoom

Pentax now offers the smc PENTAX-DA FISH-EYE 10-17mm that is made for the APS-sized sensor of the Pentax DSLR’s. It features a maximum 180 degree FOV diagonally. DCWatch has some example pictures on this page.

Links

Removing distortion with PTLens and PS Defishing the Zenitar 16mm Fisheye Lens
Wiki entry Fisheye Lens
Photozone review (EOS mount) Zenitar 16mm f/2.8 Fisheye MC
Review by Jim Tardio (Nikon D90s) Zenitar 16mm/2.8 Fisheye Lens.
Darren Gibbons’ review (D30) MC Zenitar 16mm fisheye review
Review by NK Guy (Canon EOS) Notes on the MC Zenitar 16mm 2.8 fisheye lens
A German Fisheye fanatic Fisheye & Ultraweitwinkel

It has the flare resistance of a 1970’s Led Zeppelin groupie.