[Undot]

To delve deeper into the world of tiny big I just got me an extension tube set. As I'm planning to add the Pentax 100mm macro later on I dished out some extra cash to get me, as I thought, quality ones with aperture control and electronic contacts (no AF).

My first issue is, that neither the Pentax 35mm f2.4 nor the 50mm f1.8 would fit onto it. They just wouldn't screw all the way and, of course, I didn't want to force it. Interestingly my 18-135mm mounts without trouble. Possibly something to do with the plastic mount? First setback, but I could accept that.

But the real problem is, that it would cause my display/menu/camera to go haywire. EV scale jumping around, AF metering (which was turned off as I put it into MF anyways) twitching between spot meter and something else. And when trying to access Info or Menu to adjust settings it would go there for a split second only to jump back into the main display again.
Not stacking the tubes and using only one would better the situation but not eliminate the problems.

Are the tubes (contacts) faulty? Is the K3's current too low so it won't pass through the tube bridge? Is this a known problem? Could that even short circuit my camera? I am rather at a loss and hope you can give me some insight. I'd like to have aperture control tubes as the Pentax macro doesn't, and those were the only ones I could find. But, like this, I guess the tubes are pretty much unusable and I should return them quickly.

Attached Images

   

[baro-nite]

Just a guess but maybe the mounting problems are because of getting the aperture levers crossed up. The tube has a long lever and it could flex enough to slip the wrong way.

However, the issue of messed up camera function sounds just like what I've seen with certain lens/TC combinations. I'd return the tubes.

[SOldBear]

Undot,

The tubes may short some contacts. But there is no harm to the camera. Note that the camera is designed to use old lenses (K, and even M-42 mount). All electrical contacts on the lens mount are shorted by those lenses.

Please give this a try: use a small piece of aluminum foil between the lens and the extension tube, cover the last electrical contact. In the first photo of your post, it's the contact at 8 o'clock position, next to the screw. The aluminum foil is to ground the contact, as if it didn't exist.

Do this before you attach the lens + tube combo to the camera to make sure that the piece of foil doesn't fall into the camera.

I need to dig up my notes. But I did some experiment with 7-contact vs 6-contact tubes before, and for some reason I prefer 6-contact tubes.

Edited to add:

I found it. Read this post about the differences between 6-contact and 7-contact extension tubes. I realize the 18-135mm is not a DA* as the lenses used in my test. But who knows what Pentax did.

[Undot]

Much obliged for your feedback. Thank you for that.
Extensions work with all my lenses, even a mount adapter, except for the plastic ones. Rather odd, but maybe with more testing I'll figure it out.

The tubes may short some contacts. But there is no harm to the camera. Note that the camera is designed to use old lenses (K, and even M-42 mount). All electrical contacts on the lens mount are shorted by those lenses.

Please give this a try: use a small piece of aluminum foil between the lens and the extension tube, cover the last electrical contact. In the first photo of your post, it's the contact at 8 o'clock position, next to the screw. The aluminum foil is to ground the contact, as if it didn't exist.

Knowing that it won't harm my camera is a big reassurance.
And you are correct, the menu hiccups are exactly the same as in your linked post. They go away when grounding that 7th pin. As I take it from Wikipedia the 6 pins transfer aperture information, while the 7th carries focal length, lens size, distance to subject and such "to make better exposure decisions". As I'm in manual anyways, I guess it's not much I'm missing.

Interestingly two reviewers didn't write about any such issues. But I suppose the tubes aren't faulty per se, so returning them for a replacement wouldn't change anything for me? Now I just need to decide if I should keep them with the limitations they have.

[skunktail]

I have an almost identical set of tubes, under a different brand.

I found I had to scrape off a section of the black coating on the rear (camera) side of the tube to work properly.

So, grounding is probably your issue here.

good luck

[SOldBear]

I have an almost identical set of tubes, under a different brand.

I found I had to scrape off a section of the black coating on the rear (camera) side of the tube to work properly.

Look again. How many electrical contacts do your tubes have, 6 or 7?

Different beasts, different symptoms.

[Hornet]

The Kenko auto extension tubes are the only ones I know of that have true aperture control. I don't think they are AF but that is not a useful function once a lens is mounted on tubes.

BTW there appears to be a set of the Kenko tubes for sale in marketplace at the moment (I'm not the seller).

[Not a Number]

There are the Kooka extension tubes, they have all the contacts, screw drive and even the power zoom/AF contacts:
PENTAX - KOOKA OPTRONICS CO.,LTD

Read more in this thread:
https://www.pentaxforums.com/forums/16-pentax-news-rumors/264093-new-auto-ext...-q-mounts.html

[Undot]

The Kenko auto extension tubes are the only ones I know of that have true aperture control.

I'm not sure what you mean by true aperture control. The tubes I got do handle aperture, but no idea if it's true. Thanks for the marketplace thought, too bad it's sold in the wrong location.

There are the Kooka extension tubes, they have all the contacts, screw drive and even the power zoom/AF contacts:
PENTAX - KOOKA OPTRONICS CO.,LTD

Hmm very interesting, thank you for bringing my attention to it. Sadly the UK store doesn't sell the set. But even two 25mm tubes would be cheaper with more functions, which does sound a lot better than what I got, more expensive with less functions. I think I will return mine after all and try one ore two from Kooka.

[Not a Number]

I believe SRB is selling the 25mm Kooka tube:
Pentax K Auto Extension Tube | Macro | SRB-Photographic.co.uk

[SOldBear]

I think I will return mine after all and try one ore two from Kooka.

Undot,

I don't know about the fit of the Kooka (you mentioned that your current set didn't fit quite right). But in terms of functionality, I think the Kooka behaves the same as your current set. From the photos, the Kooka has 7 electrical contacts but doesn't have the 2 power contacts.

From what I know, to avoid the "menu hiccups," the tube should either have 6 contacts, or have 7 contacts and 2 power contacts.

Note that the "menu hiccups" is not very well-known. It happens with only a few lenses (DA*, and the 18-135mm).

[Not a Number]

From what I know, to avoid the "menu hiccups," the tube should either have 6 contacts, or have 7 contacts and 2 power contacts.

The Kooka has the two power zoom / AF contacts. I posted a picture that Kooka sent me that shows the contacts.

https://www.pentaxforums.com/forums/16-pentax-news-rumors/264093-new-auto-ext...ml#post2832430



Kooka had the wrong photos up for the Pentax, they corrected it after I inquired about screw-drive and number of contacts. Looks like they messed up again. The two tube set have the screw-drive and all contacts as well.

Kooka has aboot at PhotoKina, maybe Adam will have a chance to check out the K-mount tubes.

[Undot]

Just a warning / information. It seems there's been some trouble about product quality with the Kooka tubes. Just got this from SRB:

Thank you for your recent order.

However we have discovered a fault with our recent batch of Pentax extension tubes. We have returned these to the supplier for examination.

I hope this can be resorted soon. And that they let me cancel my complete order. I don't much care for £6 of shipping costs for a £13 coupling ring...

/edit: SRB gave me a refund for the complete order - nice