Stuck Tubes - Help !

Relax, nothing off-topic or personal here! Its about stuck extension tubes . Following some of the advice I got on the thread asking about 'Pixels or Glass', wanting to take closer focused images, I got a set of 'Neewel' tubes from Amazon. First time with anything like this, so it was bound to go wrong

There the good and the bad - the good is that I was able to get shots very closely focused ans I think the quality is OK - I'll put a few shots us on another thread soon .... bad news is that one the mount rings has become stuck onto my 'M' 75-150 zoom - totally jammed.

Pictures below, but there are two mount rings, one with a small screw at the side which is the one I attached to the lens - the screw makes no difference. The aperture still works on the lens, although not 'auto-diaphragm - the lens remains fixed at the aperture on the ring and does not jump back to full open. So no 'stop down' metering, although I still get accurate readings via the green button, just a dark viewfinder at smaller apertures.

Is this functioning normal with extension tubes?


Heres the set, minus the jammed ring :





And heres the lens with the mount ring jammed :















I'm not panicking - the camera is fine (and the other ring goes on and of the camera OK) - and I can use the lens for the close-ups .... but its a nice lens and I would really like to have it back for normal shots! Any ideas very gratefully received.

About the only thing that should catch is the lens release catch.

Looks a bit like the release catch(chrome knob) is under strain. You could try gently rotating the lens and mount in opposite directions, backwards and forwards, while operating the lens release catch. Just a thought, The lens release could be a pull operation rather than a push.

Of course you may have already done this and I may be completely wrong.

If you haven't already tried this, loop something suitable round the circumference and then clutching both ends of the material (rubber is best) together try to turn the ring. With the thin metals often used on these rings finger pressure on particular parts of the circumference can cause the ring to bind.

Good luck.

The no-stopdown metering is completely normal Greg. If you buy the more expensive and harder to find 'auto' extension tubes you get stop down metering but as soon as you start reversing lenses you lose that again so the cheaper manual tubes aren't that great a disadvantage.

That silver knob on your extension tubes is the equivalent of the lens detach button on your camera body so you need to press/slide that and then jiggle the lens to detach it I guess. On cheap tubes the mechanics aren't as good as the camera body itself but I haven't had one that wouldn't release myself.

My intense sympathy- I managed to get the connecting ring stuck on my K-r by cross threading it. Took me weeks to finally get it off. i hope you have more luck. The little knob pushes down away from the lens BTW.

Best wishes,
Rob

It appears the little silver 'screw' is actually a button that operates a pin, so to release the pin you have to slide the silver button away from the lens, at the same time turning the ring to unlock it from the lens.

Nigel, in your last pic, you need to push the button towards the top of the pic and rotate the tubes anticlockwise - i.e. lift the pin, don't push it inwards.

Andrew

GOT IT !! Thank you all very much .... it was that little 'chrome knob' thing, that I didn't think was a knob at all - it is in fact a screw that come out - I was just adjusting it in and out to no effect, but as Andrew just said, it lifts up and pulls the pin up with it, therby releasing the ring. Great, I've got my lens back!

I've also now got a great set of Jessops tubes to try - interesting thing is these are more sophisticated with each having a bayonet lever - the Neewel ones don't ... what will be the practical use of this bayonet?

Thanks to all who replied - just goes to show how good this forum is ! Lucky I've stayed around

If your Jessops ones have the electrical contacts you will have to scrape away a little of the anodising on the faces of each side of each one in order to create another 'contact' since the lens mount on the digital bodies is another contact. If you have one of the plastic mount lenses you'll notice that they actually have another brass contact.

Incidentally you might get better results using a prime rather than a zoom.

Hah! - after my cracking start not being to able to get the ring off, the thought of any scraping or anodising puts the fear in me! I might hold fire for a bit ...

I've got the Tamron Adaptall 135mm f2.8, and a few test shots last nght look very sharp on that - and thats at ISO 1600 on the K7, so there's great potential there I think. Its a good focal length as well for this sort of thing. I've been enjoying focussing with live view and a magnification zoom using the info button - seems to nail it very well if I just sway my body in and out slightly. Looking forward to trying out some proper subject out in the wild.

This is one of the few uses I have found for live view

You need have no fear. Your Jessop rings do not have electrical contacts - at least, not unless I sent you the wrong set.

Andrew

Glad you're sorted!
Having bayonets between the stages makes it much easier to change the length of extension. The release leavers are also more obvious IMO.

MORE HELP NEEDED PLEASE !!

Might as well ask this here, its a related issue. Having got sorted with my stuck Neewel tubes, I have also acquired a set of Jessops ones, which are more sophisticated with a proper mount and the bayonet lever ... the Neewel ones have none of this, they just attach really.

Unfortunately I have not been able to get the Jessops ones working properly. The problem is something to do with the 'auto-diaphragm' system, because I am not getting any aperture control at all - when my 'A' & 'M' series lenses are on the tubes the aperture remains fixed at full open. I see how this is happening with the metal lever (is that the 'bayonet'?) which when moved opens the lens fully. It seems that the lever on the tubes is moving this lens lever when the lens is fully mounted and therefore locking the aperture full open.

The shots I took recently (flowers) I had aperture control because this was using the Tamron Adaptall 135mm which has a 'manual / auto diaphragm' switch ... when switched to manual I have full control, but with the tubes and the switch at auto its the same as the Pentax lenses - stuck full open.

When the lens is not fully engaged onto the tubes there is some movement of the aperture, but not when fully locked in place. Its a mystery whats going on as these Jessop tubes seem to have all the required components for proper K mount operation. Any ideas and experiences would be much appreciated - I would much prefer to keep using the Jessops tubes as they are far higher quality and more solid than the other ore simpler ones.

You will need electronic contacts for full aperture control and you don't specifically mention these.

Also, some tubes are finished in an insulating finish and the camera requires the bayonet to be an electrical contact. In this instance I have seen it suggested that scraping off a small part of the paint finish solves the problem.

Hope that helps!