I have the Nikon,50mm F1.8. I have used it on the F2 bellows previously. I only want to experiment with the extension tubes,especially as a friend offered them as a thank you for a favour I did for him. I have a Nikkor,105mm,F2.8, micro I have just acquired before Xmas so have been getting to know it over the holiday season. I will perhaps try and buy the PN-11 in the future, but they seem expensive on the auction sites.
Cliff

Cliff Newton said:
Hey guys ..I have solved the problem ! Its an F mount male adapter I need for the extension tubes. How did I find out ? ...Well we searched through my friends camera bags and found it, he had forgotten about removing the male adapter some time ago.
Thanks to everyone for your enthusiastic replies. I am new to posting in forums and am thoroughly enjoying it, but do I feel a twinge of NAS coming on ?!!!!

Do you have an older style lens to use with your extension tubes, I use mine with a 50mm F1.8
Your lens should have manual aperture control to work with most extension tubes, unless the extension tubes is a more modern style with electronic connection to the lens

Pete

I missed "lens onto the tubes" part so I presumed it was "tube to the body".
And yes in the case of 57mm body mount it is more likely some video camera to F-mount lens adapter and it is probably for focusing and not for macro, so you was right after all.

Hey guys ..I have solved the problem ! Its an F mount male adapter I need for the extension tubes. How did I find out ? ...Well we searched through my friends camera bags and found it, he had forgotten about removing the male adapter some time ago.
Thanks to everyone for your enthusiastic replies. I am new to posting in forums and am thoroughly enjoying it, but do I feel a twinge of NAS coming on ?!!!!

If it is a 57mm then you can eliminate M42 and Pentax screw mount. They're both 42mm.

I still think its a bellows for the the old pentax screw mount aka M42 ..
http://en.wikipedia.org/wiki/M42_lens_mount

something like this one? http://www.trademe.co.nz/Electronics-photography/Camera-accessories/Other/auction-260004554.htm

the adapter? http://www.rugift.com/photocameras/nikon_lens_adapter_with_lens.htm

But if it will mount an f-mount lens on the side machined into an f-mount shape, it won't mount to the body. Isn't that right? I think astrophotographer's right—it's some adaptor to let you connect an f-mount lens to a CCD camera that has a screw mount.

If you have an outside thread on the other side of the ring what you have is an reversal adapter ring.
It is used to mount the lens in reverse position for better macro IQ by screwing the lens filter thread on it.
If it is really 57mm you could try and get 52mm step up adapter to be able to mount 18mm-55mm or 50mm for example but I doubt you will find something like this because 57mm is non standard size. 58mm and 55mm are standard filter thread sizes so you better check you measurement.
One more thing, even if you manage to find an 52mm step-up adapter 18-55 or any other G type lens will be useless because you will not be able to set up aperture.

My old pentax spotmatic used to have screw mounts.. maybe that's what its for?

I will take some pics tomorrow and attach them to a reply to help clarify things a little as you suggest. Many Thanks

Can you put pictures online Cliff? That would help us out here.

It sounds like you may have an adapter to mount a Nikon lens to a specialty camera. Here's an example of one for an Apogee camera as an example:

http://www.optcorp.com/product.aspx?pid=319-327-328-9921

My friend bought them online brand new a year ago but never used them...now we know why!

You've got me there, Cliff. Maybe someone else knows why you'd make one of those without both sides being f-mount. Sorry.

Hi, Yes I can mount the lens onto the tubes but the other end has an outside thread but no adapter to enable me to attach to a D40 body. The outside thread I have only measured with a simple rule as its looks like 57mm.

I'm confused, too. Are you saying the tubes have the f-mount on only one side (you can put the lens on the tube but not the tube on the body), or that you can't mount either lens or camera?

Sorry for the confusion but I meant extension tubes NOT focusing rings. So what adapter do I need to fit an extension tube to the Nikon body ?

I never heard of 57mm thread camera mount so I suppose what you have is rare 57mm thread reversal adapter ring. In that case you need 57mm step adapter to what ever your lens filter thread is, if your reversal adapter ring has a Nikon F mount at all.
One other possibility is that you have pretty common 57mm extension ring and in that case you should tell us what camera mount looks like.

I have had a set of (unbranded aluminium) focusing rings given as a gift. I now notice they do not have the adapter to enable them to be attached to my D40 camera body. It looks like a 57mm thread but what do I ask for if I want to buy on the internet ?
Thanks in advance
Cliff