Kenko 0.16x Fish-eye Converter

"Gisle Hannemyr" wrote in message
...
I've just aquired an old Kenko 0.16x fish-eye converter with 52mm
thread.

While modern WA converters usually have no controls, this Kenko model
(long since discontinued) has /two/ control rings. The first displays
a series of decimal numbers from going 3.5 up to 90 that look very
much like aperture settings. The second is a series starting at 200
and going down to 30.

An picture of the converter, with the two control rings, and the
number series on them are at:

http://heim.ifi.uio.no/~gisle/photo/wa.html

When I experiment with these controls, they appear to control
aperture, angle of view, and vignetting - but not in an (at least not
to me) obvious way. Whatever documentation that came with the lens
is long lost.

What I want to do, is to figure out the /optimum/ setting for the
converter (ie. the setting that gives the least vignetting, largest
angle of view, and best overall sharpness. In order to do that, I
would like to know what the control rings on the converter are, and
how they are intended to be used. If anyone reading this are familiar
with this lens and its controls, what sort of prime it is supposed
to me used with, etc. - please post an explanation here.

I have had one of those (or similar) for 25 years, but haven't done any
rigorous experimentation with it. Mine was already old when I got it,
and had no documentation. It is the same as in your picture (even down
to an identical lens case) except that instead of "0.16x" it is
described as "180 degrees" (the superscript "o" is used for "degrees").
Inside the lid of the case is an alternative 49mm thread that can be
screwed on to the rear of the attachment in place of the 52mm thread.
As you suggest, the first set of numbers is apertures, and as Nostrobino
suggests, the second is for the focal length of the lens the attachment
is attached to.

I have never tried lying to the attachment about the focal length (eg,
to set it to 200 when it was actually attached to a 50mm lens), but it
appears to me that all that the second ring does is limit the aperture
(so that at 30mm the aperture range is 3.5 to 16, and at 200mm it is 22
to 90). This limiting doesn't seem to matter much if you are using a
TTL meter, but I guess it would be relevant if you were using a hand
held meter.

I have only used it with 50mm and 135mm prime lenses (I think I may have
fitted it in the distant past to both a 75-150 zoom and a 24mm prime,
but I seem to recall that the viewfinder image was so unsuitable that I
didn't take any pictures). At 50mm it is a full fisheye with a full 180
degree angle of view horizontally, and bit less vertically. There is
severe vignetting, as with an actual 180 degree full fisheye lens. With
a 135mm lens, it is a full frame fisheye, with no vignetting, beyond a
little darkening of the corners. The angle of view is obviously less,
but I don't know exactly how much less.

Image quality is not great (especially when used with a 135mm lens for
full frame). I have tended to use it 2 stops less than maximum aperture
to maximise image quality (with a 50mm lens that means f11 - with a
135mm lens it is f32, and that may explain that lower quality on that
lens), but I haven't experimented to discover whether different
apertures would be better.

--
Apteryx
Treat anger like gold. Spend it wisely or not at all.

I may be wrong here but I doubt this is an "Adaptor". It looks to me
like it is a fully functional lens in it's own right. Have you tried to
unscrew the bottom (in the picture) thread adaptor to see if it has a
Leica thread in there somewhere?

I vaguely remember seeing a fellow shooting pics for a fishing book with
one of these (or one very much like it) on an old Pentax, Spotmatic SLR.
I could be wrong so don't take my feeble memory too seriously.

Ryadia

"Ryadia" wrote in message
...
I may be wrong here but I doubt this is an "Adaptor". It looks to me
like it is a fully functional lens in it's own right. Have you tried
to
unscrew the bottom (in the picture) thread adaptor to see if it has a
Leica thread in there somewhere?

No, it's "native" thread (without either of the screw-on plates that
mine has and which give a thread of either 52mm or 49mm) is much smaller
than a Leica (I have an old Leica IIIf), or anything else I know of. I
measure it as just 28mm

--
Apteryx
Treat anger like gold. Spend it wisely or not at all.

"Ryadia" wrote in message
...
I may be wrong here but I doubt this is an "Adaptor". It looks to me
like it is a fully functional lens in it's own right. Have you tried
to
unscrew the bottom (in the picture) thread adaptor to see if it has a
Leica thread in there somewhere?

No, it's "native" thread (without either of the screw-on plates that
mine has and which give a thread of either 52mm or 49mm) is much smaller
than a Leica (I have an old Leica IIIf), or anything else I know of. I
measure it as just 28mm

--
Apteryx
Treat anger like gold. Spend it wisely or not at all.

I have an adapter like this one, it looks almost the same with a few
subtle differences. Even the case and lens cap are the same. It is
marked as being a "Spiratone fish-eye lens 0.15X". I've used it on my
Canon 50mm lens with mixed results but haven't had the time to see if
I can adapt it to the kit lens on my Digital Rebel.

Worth a try anyway!

Bob Boudreau
Canada

I have an adapter like this one, it looks almost the same with a few
subtle differences. Even the case and lens cap are the same. It is
marked as being a "Spiratone fish-eye lens 0.15X". I've used it on my
Canon 50mm lens with mixed results but haven't had the time to see if
I can adapt it to the kit lens on my Digital Rebel.

Worth a try anyway!

Bob Boudreau
Canada