Macro tubes, idiot guide please

The addition of the right tube will not affect it at all except:-

You will lose AF if the tubes do not have an AF screw coupler, and
You will of course lose infinity focus, as with any tube.

Otherwise, job done.

I can recommend Kenko tubes but you might have trouble finding them. I don't think they are made any more. They are also marked, perhaps erroneously, PK/AF, but they lack the AF coupling so its MF only.

If you find some decent tubes, ensure that they have enough contacts for modern lenses/bodies. Pentax has increased the contact count over the years. As a consequence, some older tubes with contacts may have too few.

This thread explains.

Peter job done, the tubes don't work.

If anyone wants I'll post the smaller tube with return postage for them to try and see. PM me. The annoying thing is they are nice clean tubes in a neat leather case.

Ok Doug Got the tube today - it's all fine

I think there was a misunderstanding about using the aperture...
Let me give a complete guide:

1. Manual tubes, no linkage, no contacts. You have to turn the aperture on the lens to wide open to focus, and manually turn the aperture on the lens down for metering and taking the shot.

2. Auto-tubes with linkage, no contacts. You have to set your required aperture on the lens (ie not on the camera body). While using the viewfinder the lens remains wide open so you can focus and compose. Use "M" on the camera, and press the Green button to perform stop-down-metering - you'll see the viewfinder go darker, and an appropriate exposure taken. Because the tubes have the linkage, when you hit the shutter the camera will close down the aperture on the lens and all will be fine.

3. Auto-tubes with linkage and contacts. Here, you can just use the aperture dial on the camera as before! You leave the lens on the "A" setting, or you can use lenses that don't have an aperture ring (like the DA17-70 etc). The camera can control everything because it 'knows' what the lens is.


So, Doug, you have option (2). You should set the Nokton to an aperture other than A (e.g. f/, and when you hit the Green button then the lens should stop down and meter.

This behaviour is exactly the same as if you have NO tube, but with the lens on an aperture other than "A".

Let us know if that works now that it's been explained!!

Matt

Nope, I think I understand but the camera and tube don't.

2) FA Lens on the tube, lens&tube on the camera, adjust lens to F16, no change to size of aperture either when pressing green button or when shooting.

Lens works as expected on its own. On the tube, as you click the bayonet the aperture goes wide and stays wide. Adjusting the aperture ring, pressing the green button, shooting do nothing to the aperture, even set at F16.

Cheers

OK folks, Matt has replicated the tube issue and has identified (I hope )the reason. Once a fix has been tested we can reveal the problem. The probable cause is the K-7 being too clever by half. (thankfully my idiocy is back to normal levels).

OK marvellous macrolicious Mattmatic is correct and has solved the riddle.

The Vivitar Automatic Extension Tube is coated in a lovely black paint. The paint is all over the surface of the tube.
The paint covers where the K-7 body touches the electronic contacts and acts as an insulator. Sooooooo the contacts, dont! And the K-7 body, clever little thing, doesn't know anything is there, and doesn't do anything.

Scratch off the paint and allow the contacts (not sure which so I did the lot) to contact and .... Whoop de dooo. Whizz burrr. Press the green button and the aperture of the lens closes down to meter scene. I'm also going to guess that you need to make sure the metal bayonet makes a contact with the tube fitting a kind of earthing to the body.

Problem solved.

So if you have a problem with your K-7 in manual with macro tubes not stopping down correctly, remove(carefully) any paint that may be insulating the tube from the contacts on the K-7 body.

e.g.
[IMG]http://i740.photobucket.com/albums/xx49/df8/IMGP0149.jpg[/IMG]

Cheers Matt.
Rough and ready FA28-80 at 32mm (guess)F9.5, 36mm Tube.

This is ebay
[IMG]http://i740.photobucket.com/albums/xx49/df8/IMGP0141.jpg[/IMG]

A bit more work and I have a miniature world of fun awaiting in my days off. (no my wife is not away)

(BTW: the *ist-D did not have a problem and worked fine with the tubes paint on)

Hey Guys,

Been removing paint from my extension tubes in order to fix this problem, but even after removing paint, I still have the problem.

The pictures above are no longer available, could anyone re-upload the pictures to show where paint must be removed from?

Thanks

I can't find my original post where I identified this problem and recommended a fix for it, but here's a thread with a photo from another satisfied user.

Nice to see you posting again Peter .. thought you had gone walkabout.

Wonder what happened to Clarky.

Hi Mike,

I've taken some time off from forums lately and I've not touched the camera since Three Kings. I'm not sure I'll be as prolific a poster as I once was, but I'll be around.

Clarky hasn't done much anywhere for some time. His Flickr account is stagnant too. I guess we all move on from time to time.

I've been trying very hard to resist your Siggy 50-150mm 1:2.8 lens, and succeeding . . . so far.

Cheers.

Thanks chaps, this was useful. I dont have any contacts at all on my tubes (Vivitar AT-22).

I feel my problem is that I need

1) Electrical contact through the tube for the 7th contact as shown in the link (done)
2) I also need the 3rd body contact depressed, so that the camera is happy to issue aperture commands to the lens via the tube aperture levers. The Jessops tube referred to here have a ball contact to do this, but the vivtar tubes have none.

It's point 2) where these tubes seem to be failing, so what do I need, a thin ring with a nobble in the right place to depress the 3rd contact, that fits between tube and camera body?

These contacts are not switches that need to be depressed, they are simply a spring loaded ball bearing which mates to a corresponding flat contact plate.

The contact must therefore be continuous, or not, through to the camera body.

If your problem is that a ball ended contact on your lens is electrically connected to the tube body, insulate it with something. I don't recommend any adhesive backed product applied to the lens as you'll soon have other problems with the lens, but you can stick a piece of electrical tape to the tube body to provide the insulation if that is what is required.

The only real answer to this issue is to get a set of tubes having all the necessary contacts. The number of contacts varies with the age of the tubes of course, just as it did with the KA mount, hence the need to create a pseudo contact with older Jessops (and other makers) tubes by scraping some paint from where the additional contact is on newer tubes. So beware, get a set having all 7 (I think) contacts.

OK thanks for your input Peter, now that I am aware of the limitations of the setup I can start to use them accordingly. TTFN!