Help needed with Vivitar Auto Extension tubes

Hello,

I recently picked up a set of pristene Vivitar AT-22 Auto Extension Tubes to use with my K7 and an A 50mm 1.7.

Unfortunately I hadn't realised that without the electrical contacts ( as fitted to the AT-23) the tubes won't work correctly as the mounts are painted and not bare metal. Hence they won't allow stop-down metering with the green button.

I have read here that it's possoble to remove some of the paint from the mounts on the tubes to short out some of the contacts and subsequently allow stop-down metering.

Does anyone have any details as to how much paint needs to be removed and from exactly where on the mounts?

Thanks

LINK

John

Thanks for the link John.

Unfortunately my tubes don't have any contacts at all. Do you know if it is still the same area that needs to be removed?

With extension tubes 'Auto' usually only means that they operate the iris automatically.

Without any contacts you will have to use stop down metering. Scraping paint off will do nothing unless you have the full set of electrical contact.

Unfortunately it's the stop-down metering that I'm having the problem with.

The attached lens is being held fully open regardless of the aperture ring position. When I stop-down meter with no tubes attached (just the lens) it works fine and I can see the lens closing down. However when I attach the tubes the lens stays fully open.

I have found this thread

link

Unfortunately the photos of the paint removal are missing from the thread.

You wouldn't have a problem with metering with the lens only attached as it has the "A" setting.

Are you working in Manual, having set to allow use of the aperture ring?

Here is a link to how I set up my K-x. Presume the K7 is similar

http://support.pentaximaging.com/node/1

Yes - I have selected "aperture ring permitted" and as mentioned the stop-down metering works fine when the lens is attached directly to the camera. It just doesn't work when the extension tubes are between the lens and the camera.

This is a Jessops set, does yours have a similar set of contacts?

[IMG]http://i679.photobucket.com/albums/vv154/bforbes/IMGP5907.jpg[/IMG]

I have the jessops set with the through contacts as above.

It's important to note that the mount ring is also a 'contact' providing a return path for the circuit created by the aperture contacts

The Jessops rings have painted or anodised mount rings and thus won't work unless you scrape off some of this coating and allow electrical continuity. At least that was the case with my set. I used emery paper, and made suer I blew off any residue before using them on the camera and lens.

Mine are second hand so I'm not sure what the original owner has done to them. However there is no sign of the paint having been removed from anywhere and they work fine.

There must be some electrical contact between the lens mount and the camera body for it to work somewhere. I only discovered this because my 50mm/f1.2 has only one aperture contact pin, so the only way to make the circuit was through the bodies.

Problem now solved - thanks for all your suggestions.

Having read somewhere that removing some of the paint in the area where the electrical contacts would connect I bit the bullet and started to scrape off paint.

Sure enough they now work! I've repeated the process for all 3 tubes in the set and the stop-down metering now works for the tubes in combination or individually.

Hey guys, having the same problem with my K-r and a set of Vivitar AT-22 extension tubes.

Saw this thread and a few others suggesting removing the black coating around the area which contacts with the electrical contacts on the camera body. However, the problem remains.

Could anyone post a picture of their tubes showing the places where the black coating has been removed?

THanks

Paul

Hi Paul,

Here's a photo showing the area of paint I removed from mine.



Vivitar K mount extention tube by Mark B Images, on Flickr

The lens on the left is the A 50mm 1.7 that I use with the tubes. I compared the 2 mounts and removed the area of paint where the A contact is.

You do need to have the "use aperture ring" (or the Kr equivilent) set to permitted in the menu and use the camera in M mode.

I hope this helps

Thanks for your quick reply Mark.

Your image is very useful, I have done something very similar, but have extended my emery work down a little further, to where the lug (at 3'o clock position) starts.

Despite this, I cant get the thing to work as expected.

So, just to check I'm not being dense, here is my sitation:

Pentax K-r, DA L 18-55mm Kit lens, Vivitar AT-22 extension tube set

When the extension tube is connected, the aperture of the lens remains fully open at all times, either when doing optical preview with the Green button, or when taking a photo. The aperture indicator reads F -.-

Removing the black layer as you have done would allow electrical contact with all camera body contacts (it seems this is important as the 1st contact appears to require contact).
However, this does not work for the 5th contact (working clockwise from 6'o clock position on the body). This 5th contact is recessed, and requires a convex contact from the lens to tell the camera that aperture settings may be controlled automatically. As you know, while most lenses will have such a contact, the extension tubes have not, and I feel this is the problem.

This idea is supported by the fact that I see the exact same behaviour if I attach a lens with an aperture ring set to anything other than 'A', (this retracts the lens contact from the 5th position). This suggests to me that when the tubes are attached, the 'A' contact on the body is not engaged. And consequently I have no aperture control.

So am I expecting to much here? Do you have control of your aperture with your setup? or do you make do with full open aperture?

Apologies for long post

Thanks