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03-24-2009, 09:59 PM   #1
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Kenko Fish-Eye 180 adapter

Rather than spewing advice and observations, as usual, I now humbly solicit comments (other than YOU FOOL!) and advise (other than TOSS IT!) about a chunk of glass I acquired today, labeled KENKO FISH-EYE 180 (degree) No. 65138. I probably overpaid - don't ask. I was under no illusion as to its edge sharpness, but I'm having some issues with it.

Yes, I searched here, and the rest of the web, for details and maybe a user manual, and found little of substance. I know this was often rebadged, but I haven't searched under all possible names. Should I bother?

The fisheye sports two rings, one marked with f-stops (3.5-90), the other with focal lengths (30-200). Apparently the host lens should be wide open; the first ring sets the aperture; the second ring should be set to the host lens focal length (but actual, or with crop factor?), and limits the f-stops available. These may have some influence over vignetting and edge trim, but just HOW isn't yet obvious.

The Kenko screwmount is about 22mm, and it came with 49mm and 58mm adapter rings, for mounting on the front of other lenses. Apparently a 52mm ring was also common, but not in this package. I'm rather in adapter hell right now, having left most of them at my faraway house during this trip, so I'm rather limited as to the lenses I can mount this on.

So. I try it on some lenses with 49mm filter rings. On anything 37mm or shorter, the image circle comes nowhere near filling the K20D frame's short dimension. With 50mm or longer primes, the image circle edges are cropped. This suggests that for frame-filling, a 43 or 45mm prime is needed - which I ain't got and won't buy just for the Kenko. All I want is a nice 180 circle on the frame - is that too much to ask?

Curiously, when mounted on my Pentax-M 40-80, the image circle best fits the frame at around 55mm. I thought maybe the distance from the Kenko to the host's front element might affect image circle size. But adding an 8mm-thick ring between the Kenko and my FA 50 doesn't seem to affect that, not that I can tell. Curious. Or maybe I'm not looking closely enough.

Anyway, in the light of day tomorrow, I'll try that zoom+fisheye combo, a bit hefty at 650g and 150mm long x 65mm thick. It would be nice to have the right (light) prime. But Santa Claus isn't due for awhile. Does anyone here have any useful (bitter?) experience, hard facts, insights, a user manual, anything to help me decide whether or not to drive 30 miles to Ft Huachuca to try to get a refund? Thanks.

03-25-2009, 03:57 PM   #2
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Here's an update, 1/2 day later: Even though I overpaid (NEVER ASK!) I'll keep the bugger. For a full circle image on my K20D, it seems to work best at 40-43mm - and me without a FA 43/1.9. Does anyone have a 43mm lens with broken aperture/AF/whatever but clear optics, that they'd like to sell cheap? Yeah, I've put that request in the Marketplace. And I'll try it on 135-200 teles to eliminate vignetting but I won't expect much IQ.

At 43/2.8 on my Pentax-A 40-80/2.8-4, I find:

* The Kenko should be stopped to at least f/16. The longer the lens, the smaller the stop, all the way down to f/90. which I'll try Real Soon Now.
* So far, the edges are always fuzzy - maybe a thick 58mm ring will sharpen that? Sharpness near the center ain't bad.
* Image stabilization should be OFF. With IS and LiveView, the image floats all over the LCD screen! With the Kenko mounted on a DA 50/1.4, the K20D shook like a jumping bean!

It's good to stick into round openings, or real close to acquiescing faces, etc, but note that it is VERY slow. It should be fun for all-sky shots, midnight flyovers, overhead thunderstorms, UFO invasions, et al. I still have much to try and learn, and I haven't even applied any PP tricks yet. Stay tuned.

Like I said on another thread, you can paint with a fine brush or a pallette knife; you can sculpt with a fine chisel or a chainsaw. Bugeyed adapters like this are the pallette-knives and chainsaws of the photography world, to be used with enthusiasm and indiscretion and humor.

Last edited by RioRico; 03-25-2009 at 04:51 PM.
03-27-2009, 08:38 AM   #3
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Hi RioRico! Got one of these Kenko's myself. It was supposed to make a circle when used with a 50 mm normal lens in the days of fullframe. Used on a digital SLR that would mean a lens around 31-33 mm if your sensor is half the size of 24x36. The dual scales is confusing at first but in reality they're just a convenience if you want to make exposure calculations. They don't afflict the exposure a bit, just there to show that the lens gets slower used with a longer lens. It's the fat black ring that does the trick and controls the diaphragm. And yes, the host lens should be used wide open although that's open to experimentation. I used it on Topcon and Nikon lenses. Also have a look on the Belarusmade Peleng 8 mm fisheye, fun and quite cheap!
Have fun!
04-02-2009, 11:52 PM   #4
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Hi Nollberga! With the APS-C crop factor of 1.5 or so, I'd expect the image circle to be cropped with a 35mm lens, but I tried 35mm and 37mm lenses, and a zoom at 40mm, and found the circle to be much too small. 43mm works best. Go figure! I'd suspected the focal-length ring to be informative instead of functional - at least it's slightly more useful than a phony 'aperture' ring on a teleconverter I once had. As time becomes available (soon!) I expect to engage in extensive experimentation, probably injuring my sanity in the process. No loss.

04-03-2009, 08:25 AM   #5
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KENKO = Hoya = the owner of pentax btw :P
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