Macro tubes, idiot guide please

OK, I have macro tubes and put the Nokton on the front , K-7 on the back.
How do I get it to close the aperture?
It seems to be shooting wide open and the image is soft.
It might be a stupid question.
I have it in Manual exposure mode.

[IMG]http://i740.photobucket.com/albums/xx49/df8/IMGP9324.jpg[/IMG]

Thanks

I'm not familiar with the Nokton but isn't there an A setting on the aperture ring followed by 2, 2.8, 4 etc?

In that case to set the aperture manually you get it off A and onto the f stop you want. There may well be a button to press to get it off A.

Proceed with caution!

Mike

I see what's happening. There is a linkage through the tubes to the aperture. I can set the aperture but when I mount the tubes the aperture is opened up wide and doesn't close. Even when set to F16.

The display shows F - - .

Do I need tubes without the aperture linkage?

In that case I'm not sure. If it's showing F-- then I think that means the camera can't work out what the aperture is and can't control it. I think what I suggested should work. I get F-- when I use my lens baby which has no aperture contacts.

Do your tubes have the electrical contacts?

Mike

Does sound like there's a problem with your tubes - try the tube with the kit lens instead of the Nokton, see if there is any communication or not.

I have an old Vivitar x2 TC with the electrical contacts as well as the mechanical lever, but when it came (for £5!) it didn't work and said F--, but after I took it apart, fiddled with it a bit, and put it back together again, it worked.. Works even better after I took all the glass out and it became a 24mm Auto Tube instead!

Short version - you need electrical contacts as well as the mechnical lever for the camera to be able to control the Aperture. Otherwise you will need to set it on the lens by hand (hardly the end of the world when it comes to Macro photography...)

Hi
You may have manual extension tubes as opposed to auto extension tubes. I this is the case you will need to enable use of the aperture ring in the camera's set up menu and use stop down metering to obtain a correct exposure.

John

If the extension tubes have the electrical contacts on each tube then you can use the lens in "A", and adjust aperture from the body.

If the extension tube has no electrical contacts then you'll have to do stop-down metering - by setting the aperture manually on the lens. By default the body will show "F--" to warn you. There's a custom option to allow manual aperture selection, and then the "F--" won't show

If the extension tube has a mechanical 'finger' that slides then it's called "auto" extension tubes - you can select the aperture and use the Green button in "M" mode to perform automatic stop down and meter on the K20D & K7.

So, summary - there are FOUR types of extension tubes as far as I know:

1. Manual. No electrical contacts, no 'finger' linkage

2. Auto with no electrical contacts. Includes the 'finger' linkage to control the aperture blades on the lens.

3. Auto with electrical contacts (also includes the 'finger' linkage)

4. Auto with electrical contacts including the power zoom connections (which may, or may not work with SDM lenses).

Hope that helps!
Matt

Thanks folks. You are better than google or wiki.

OK Nokton has aperture setting and A.
Set to F8.

Scenario is as Matt lists 2.
Finger linkage to control aperture (no contacts).

Putting the lens on F8 in to M mode.
Press the green button and whizz burr , hey presto sounds like its doing what it should. I now understand the "stop down metering". The camera takes the aperture from wide open to the set aperture meters and then opens back up.

I know everything must be OK as it is with the lens.
Stick a tube on and nada/ nothing.
Vivitar Auto Extension Tubes.

I suspect there is a linkage issue with the body.
I suspect saving for a Macro lens will be easier.

You can easily check whether the stop down linkage is working

Look at the front element when you do the green button - compare at f/11 and f/4. (Also the exposure should change.)

There is always a reason for extension tubes, even with a macro lens (Extensions + Macro Lens = incredible close ups).

...in fact, you can always reverse an old lens as well for super macro...

Matt

This is a very useful topic, and the answers will help me as well, thanks everybody.

Matt, it would be OK but the tubes are holding the aperture open full, even when set to a particular setting. Stuck open when attached at F1.4.

I could mutilate the mechanism, but I think I'd rather pass them on to somebody who can use them properly and I'll do more research and get a more suitable tube set (with contacts). Or I'll save for the last reasonably priced Pentax lens, DFA100mm.

I've tried with a FA28-80mm and as you mount the lens/tube the aperture widens out and doesn't budge. Lens alone and AOK, stops down fine in manual mode on the green button. Its not the camera or lenses.

The only thing I can see is there are a few mm of travel before the finger engages the aperture, with the tube attached. On the MZ-M you can see its detecting the correct aperture as the ring is turned. Its the release finger which must be operated before the shutter is released that seems not to work.

Lens only, as soon as the finger is pushed the aperture changes.

I give up and will find another tube set (known to work with the K-7) or pawn a cat for a DFA100.

Lenses both Nokton and FA stop down as expected on their own with the K-7, in Manual and green button.

From what I have read here, it would seem that:-

1: Your tubes have no contacts, and
2: Your tubes have the mechanical coupling to stop down the aperture, and
3: Your lens has electrical contacts

If that is correct, you should be able to use your lens/tube combination as if they were a Pentax M series lens or earlier. This should allow the lens/body to use the auto diaphragm capability of manual lenses. That is, the body can control the aperture of the lens by a mechanical linkage.

To test:-

1: Set the camera body to exposure mode M - manual.
2: Ensure you have enabled the use of the aperture ring in the custom menu.
3: Set the aperture on the lens to a small aperture (big number), f22 or similar.
4: Press the green button but as you do so, look into the front of the lens where you should see the diaphragm/iris close, and open again. This action should set a shutter speed that is appropriate to the aperture to give a correct exposure value.
5: Change the shutter speed manually to a duration of 1 second or so. We are only testing the mechanics here, you will not get a correct exposure.
6: Still looking into the front of the lens, take an exposure and observe the diaphragm/iris. It should close for the duration of the exposure, then re-open to full aperture.

If the mechanics works as I have described, all would seem OK.

Now choose a subject, set an appropriate aperture for the required depth of field, repeat steps 4 & 6, omitting step 5, and point the lens at your subject, not yourself. You should now have a correctly exposed image of your subject.

Doug, I would persevere for the moment, as for whatever reason Pentax fit extension tubes with electrical contacts are extremely rare.

There is a Polish outfit who sometimes sell new ones with contacts on ebay, Kubisek I beleive is the brand name, for rather a lot of money (close to £100 if I recall correctly). There aren't any at the moment (which seems a bit odd, normally there are 3 or 4).

Peter,

All tried and tested, lenses pass and tubes fail.
I'm now happy I understand stopping down.
I'm happy I can see the difference the electrical contacts make for the FA lens vs the lack of contacts on the Nokton.
Apperture OK enabled in menus.

Lenses Pentax and Nokton tested and stopping down correctly as Matt and you describe.

Put them on the end of a tube and the aperture is held wide open.
The aperture sense linkage is working as on the MZ-M I can see the Tv change as I dial in the apertures.

But with the tube on , everything stays wide open. No stopping down.
No wizz whir with green button unlike the lenses on their own.

I'll have another look another time as the day off is no longer my own.

(Recuperating cat, wife, doctors, meal out ... damn life getting in the way of photography)

Final thought, if I have the K-7 and FA-28-80mm stopping down correctly, the addition of a tube should not affect it?