Kenko 0.16x Fish-eye Converter

L x D, W: 87 x 58 mm, 265 g.

I have been able to find out very little about the Kenko 0.16x fish-eye converter except that is was used as a prop as the “eye” of Hal in Stanley Kubrick's: 2001 – a Space Odyssey. Since the film was released in 1968, it must be older than this. It was also traded under the names “Rikenon 0.15x fish-eye” and “Spiratone 0.15x fish-eye”. While the conversions factors and names are different, they are optically and mechanically equivalent. The Rikenon and Spiratone versions are just re-branded Kenko converters.

From 2001: A Space Odyssey, featuring Kenko 0.16x Fish-eye Converter as the “The Eye of Hal”.

It has been discontinued a long time ago. I bought my sample in mint condition in 2006 on eBay. If you want this converter, your best bet is probably to search eBay for Kenko or Spiratone fish-eye. (Note: There are also some brand new pseudo fish-eye converters carrying the Kenko brand offered on eBay. These modern designs are inferior compared to this antique and IMHO not recommended.)

Below is a photo of my converter along with the original leather case and lens cap.

Kenko 0.16x Fish-eye Converter, case and lens cap.

My converter has a detachable rear plate with male 52 mm filter threads, which also happens to be the standard filter diameter on “normal” Nikon lenses. When the device was current, you could buy plates with 46, 49, 52, 55, 58, and 62 mm threads.

Converter attached to a 50 mm primary lens and mounted on a Nikon F90x.

It has a huge, bulging, front element. The front element is very exposed and you need to be careful when carrying this around. With a 180° field of view, you cannot use a lens hood, and there is of course no way to fit a filter for protection.

Construction

The construction contains a lot of glass and metal, and it is quite heavy (265 grams). I do not recommend attaching this to cheap plastic lens, at it may put enough strain on the tube and mount to break something.

While modern wide angle attachments usually have no controls, this Kenko model has two control rings. The first displays a series of f-stops, going from f/3.5 up to f/90. The second is a series of focal lengths for 35 mm camera lenses – starting at 200 and going down to 30.

The first ring controls a mechanical aperture diaphragm inside the converter. It lets you control the amount of light transmitted by the converter. The sole function of the second ring is to limit the range of aperture settings available. Setting it to 30 mm makes the aperture range is f/3.5 to f/16. Setting it to 50 mm makes the aperture range is f/5.6 to f/22. Setting it to 200 mm limits the aperture range to f/22 to f/90.

I assume that you are supposed to set the second ring to match the actual focal length of your primary lens, but it does not seem to matter much if you “lie” – at least not with the focal lengths I have used.

Optical characteristics

I now only use this converter on a camera with 135-format film and an FX-sized sensor (i.e. Nikon F90x and Kodak DCS 14n). My preferred lens for this converter is the Nikkor 50 mm f/1.4 AF-D. Aperture mode works fine for exposure control. Autofocus don't work. In fact, trying to use autofocus with this converter was a great source of frustration (and a lot of blurry images). What works is to set the primary lens to infinity, and just forget about focusing.

In the image below. the distance from the front element of the converter to the nearest flower was around 10 cm. The prime was focused at infinity with the aperture set to f/1.4. The converter was stopped down to its minimum aperture for a 50 mm prime: f/22.

Flowers. Distance from front element 10 cm. Prime focused at infinity and @ f/1.4 Converter @ f/22.

Setting the 50 mm to any other distance than infinity results in less sharp images. Setting the 50 mm to its closest focus distance (45 cm) gives a sharp image of the dust inside the converter.

The colour rendering of the converter distinctly warm. Putting the converter in front of the 50 mm, daylight (clear sky) shifts from 5000 Kelvin to 4100 Kelvin.

White balance: Left, without converter (5000 Kelvin). Right, with converter: 4100 Kelvin.

I've corrected the white balance of all the other images in this review in post-processing.

The converter is not immune to flare, ghosting or chromatic aberrations. To be fair, I had to pixel peep at 300 % to see the in the centre of the image CA clearly. Around the periphery, CA in the form of a bright blue halo, is present in almost every image.

Flare and ghosting? Yes (left). Chromatic aberrations? Yes (right, 300 % crop).

I have found that I get best results when I set the aperture on the converter and leave the primary lens open. Stopping down the primary will result in vignetting.

Stopping down the primary lens results in vignetting.
Kodak DCS 14n (FX), Nikon 50mm @ f/16, Kenko Fish-eye converter @ f/22.

For best results, I need to open the primary lens to is widest aperture, and stop the adaptor down as far as the 50 mm range permits (f/22). These are the settings used for the image below.

Kodak DCS 14n (FX), Nikon 50mm @ f/1.4, Kenko Fish-eye converter @ f/22.

As you can see, the result with this combination is a typical fish-eye “look” with circular vignetting. It provides a full 180 degree angle of view horizontally and vertically.

Sharpness is fairly good in the centre. The edges are adequate for web resolution, but they are soft if you pixel-peep or enlarge to A4 size, as the 100 % crops below show:

100 % crops from the image above. Clockwise from top left: left, right, centre and bottom.

A fish-eye is a fun lens. With it, you can create images with wacky perspectives and unusual angles. An example is the image below, that somebody suggested should be titled “housing bubble”.

Housing bubble.

Below is another example. Here I've used the fish-eye converter to create a caricature self-portrait. With a cheap converter like the Kenko, you can have some of fish-eye fun without paying too much.

With a fish-eye, you can create caricature portraits.

I also tested the converter briefly on a Sigma SD10 DSLR. This camera has a 1.7x smaller sensor than FX, so I tested it using a 28 mm lens as a prime. This also produced a 180° circular image with a fish-eye perspective. Provided you have a suitable primary lens, this converter should work fine on DSLRs with APS-C, DX or Four-Thirds-sized sensors.

Conclusion

The combination of a 50 mm “normal” lens on a 135-format film camera or a DSLR with an FX-sized sensor and this converter will yield a circular image with a full 180° circular field of view, just as a regular fish-eye lens. It also works on DSLRs with an image circle smaller than FX, provided you use a primary “normal” lens with a focal length that compensates for the crop factor.

Fitting it to wider lenses is possible, but only results in a smaller image circle. Fitting it to the front of tele lenses between 135  and 200 mm may result in a rectangular fish-eye, with no corner vignetting, but with some edge softness.

It only gives acceptable results when used with a good primary lens with “normal” fixed focal length. There is no point in using this with a zoom.

While this attachment is not a substitute for a real fish-eye lens, the image quality is acceptable for use on the web and for printing on postcard sized photos. If you enlarge photos taken with this converter to A4-size and larger, you must expect some softness.

This converter may not be for everyone, but if you already have a decent “normal” lens and can find one of these at a sensible price, it will let you play with the 180° fish-eye “look” without having to spend three digits on glass.

Postscript: How not to use the attachment

I have never had a manual for this attachment, but I have been advised by the seller to attach it to the front of a 50 mm “normal” lens on a 135-format film camera or digital with an FX sensor. This combination would produce a circular image with a full 180° circular field of view, just like a regular fish-eye lens.

At the time of purchase, I did not own any of the recommended equipment. So the first thing I did was, of course, to ignore this advice. Below is my findings from these experiments.

Compact experience: Putting the Kenko attachment on a Canon Powershot G5 with a 4x zoom was a disappointment. Best results with the attachment was achieved with the G5's prime was zoomed to its tele end – 28.8 mm (~139 mm) – which means that after adjusting for the 0.16x fish-eye factor, the resulting focal length is 22 mm. This results in a fish-eye “look” – sort-off, but with an angle of view of no more than about 120 degrees. Zooming the G5 out to wider focal lengths just results in a smaller image circle with no increase in angle of view. I haven't tried it on a compact with a fixed focal length lens, such as the Ricoh GR Digital, so I do not know whether this will give better results.

Canon Powershot G5, 28.8 mm with converter.

Zoom experience: I tested the converter on several zooms, but with poor results: Massive vignetting occurred (see sample below, from a Nikon 35-70mm zoom). I concluded that this converter should only be used with fast lenses with fixed focal lengths.

Vignetting when using the converter on a zoom set to 50 mm. (image circle indicated with red ring).

Telephoto and wide-angle experience: Fitting it to the front of tele lenses results in a rectangular fish-eye. The image below show it attached to a Nikon 105mm lens. The image is almost rectangular. Unfortunately, the edges are soft even at the web resolution.

Using the converter with a Nikon 105mm on a Nikon F90x results in an almost rectangular image.

Attaching it to something like a 135 mm lens should result in a completely rectangular image with no corner vignetting. However, the edge softness makes this an unattractive combination.

I also tried attaching it to wide angle lenses, but this only resulted in a small image circle, and otherwise identical results to what I got from using it with a 50 mm lens.