Zenitar 16mm on Spotmatic F?

iht · 09-09-2010, 01:08 AM

I just came across the following link that states it's not possible to use the Zenitar fish eye on the Spotmatic F:

Asahi Pentax

I presume that's due to the open aperture metering? Can anyone else confirm this?

Thanks.

**interested_observer** · 09-09-2010, 07:23 AM

I might be showing my ignorance here, but I believe the Spotmatic F is a M42 camera mount (my IIa is but not familiar with the F model). The Zenitar is a K mount lens (for pentax). I do not know of a "reverse" m42/K mount adapter (allowing a K mount lens on a M42 camera. Given the registration distance and the mount's physical radius (the m42 adapter fits inside the K mount structure), I do not believe its mechanically possible.

noblepa · 09-09-2010, 07:34 AM

Originally posted by iht

I just came across the following link that states it's not possible to use the Zenitar fish eye on the Spotmatic F:

Asahi Pentax

I presume that's due to the open aperture metering? Can anyone else confirm this?

Thanks.

I can't confirm this, because I don't have that lens. However, I don't think that open-aperture metering has anything to do with it. The Spotmatic F will do stop-down metering just fine, if the lens lacks the additional linkage for the aperture.

I suspect it is more likely that the rear element of the lens extends too far into the camera body, and interferes with the mirror operation. When the original Spotmatic was released, along with the 50mm, f/1.4 Super Takumar, that lens wouldn't work on some H3v/SV models (Spotmatic predecessor), for this reason.

Or, it could be as interested_observer suggests: it is a k-mount lens. While there are plenty of adapters to allow you to use M42 screw-mount lenses on k-mount bayonet cameras, I know of no adapter that will allow the reverse.

stevebrot · 09-09-2010, 08:00 AM

The Zenitar 16/2.8 Fisheye is available in M42 screw mount and should work on the Spotmatic F in stop-down mode the same as other non-SMC M42 lenses using the meter switch on the body. Note, however, that the M42 Zen is not compatible with K-mount cameras unless it has been surgically altered to make the aperture fully manual (no A/M switch on lens).

Whether there is physical interference with the mirror is another matter. I have the K-mount version of the Zen (same registration distance) and it functions quite nicely on my Pentax KX. The KX is supposed to be very similar to the later Spotmatics, but I can't say for sure. All I can say is that the rear intrusion of my Zen does not appear to be severe and is no worse than my various M42 lenses. As always, YMMV...

Steve

Last edited by stevebrot; 09-09-2010 at 08:11 AM.

iht · 09-13-2010, 03:30 PM

Thanks for that guys.

I have the M42 version, and I manually took out the aperture pin, so it's always stopped down to the actual aperture, so that's not an issue on K mount camera.

Hmm...I'm just a bit scared to try it on still....can anybody confirm the rear protrusion thing?

09-09-2010, 01:08 AM	#1
iht Veteran Member Join Date: May 2009 Location: Sydney, Australia Photos: Gallery Posts: 528	Zenitar 16mm on Spotmatic F? I just came across the following link that states it's not possible to use the Zenitar fish eye on the Spotmatic F: Asahi Pentax I presume that's due to the open aperture metering? Can anyone else confirm this? Thanks.

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09-09-2010, 07:23 AM	#2
interested_observer Loyal Site Supporter Join Date: Jun 2009 Location: Tumbleweed, Arizona Photos: Gallery \| Albums Posts: 5,707	I might be showing my ignorance here, but I believe the Spotmatic F is a M42 camera mount (my IIa is but not familiar with the F model). The Zenitar is a K mount lens (for pentax). I do not know of a "reverse" m42/K mount adapter (allowing a K mount lens on a M42 camera. Given the registration distance and the mount's physical radius (the m42 adapter fits inside the K mount structure), I do not believe its mechanically possible.

09-09-2010, 07:34 AM	#3
noblepa Veteran Member Join Date: Sep 2007 Location: Bay Village, Ohio USA Posts: 1,142	Originally posted by iht I just came across the following link that states it's not possible to use the Zenitar fish eye on the Spotmatic F: Asahi Pentax I presume that's due to the open aperture metering? Can anyone else confirm this? Thanks. I can't confirm this, because I don't have that lens. However, I don't think that open-aperture metering has anything to do with it. The Spotmatic F will do stop-down metering just fine, if the lens lacks the additional linkage for the aperture. I suspect it is more likely that the rear element of the lens extends too far into the camera body, and interferes with the mirror operation. When the original Spotmatic was released, along with the 50mm, f/1.4 Super Takumar, that lens wouldn't work on some H3v/SV models (Spotmatic predecessor), for this reason. Or, it could be as interested_observer suggests: it is a k-mount lens. While there are plenty of adapters to allow you to use M42 screw-mount lenses on k-mount bayonet cameras, I know of no adapter that will allow the reverse.

09-09-2010, 08:00 AM	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	The Zenitar 16/2.8 Fisheye is available in M42 screw mount and should work on the Spotmatic F in stop-down mode the same as other non-SMC M42 lenses using the meter switch on the body. Note, however, that the M42 Zen is not compatible with K-mount cameras unless it has been surgically altered to make the aperture fully manual (no A/M switch on lens). Whether there is physical interference with the mirror is another matter. I have the K-mount version of the Zen (same registration distance) and it functions quite nicely on my Pentax KX. The KX is supposed to be very similar to the later Spotmatics, but I can't say for sure. All I can say is that the rear intrusion of my Zen does not appear to be severe and is no worse than my various M42 lenses. As always, YMMV... Steve Last edited by stevebrot; 09-09-2010 at 08:11 AM.

09-13-2010, 03:30 PM	#5
iht Veteran Member Join Date: May 2009 Location: Sydney, Australia Photos: Gallery Posts: 528 Original Poster	Thanks for that guys. I have the M42 version, and I manually took out the aperture pin, so it's always stopped down to the actual aperture, so that's not an issue on K mount camera. Hmm...I'm just a bit scared to try it on still....can anybody confirm the rear protrusion thing?