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04-27-2012, 10:18 PM   #1
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TTL meter not responding with Extension tubes

Just purchase some pentax 6x7 auto extension tubes and when I mount the lens and try the meter it does not respond. I notice that on the lens there is an aditional leaver sticking out that moves something that moves the chain that is attached to the meter (?). Not sure if themeter is ment to work, but from accounts from a google search it seems the meter should work. Just wondering if anyone has some advice or I am doing something wrong.

much appreciated.

Fabian.

04-27-2012, 10:43 PM   #2
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If it's the 6x7, I believe you need to use the stop down lock on the lens to initiate metering, and metering will be done as stopped down.
It's been years since I've used my 6x7, so I could be mis remembering.
04-28-2012, 08:20 AM   #3
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Wheatfield is right.
The aperture postion is not detected with auto-tubes, only the auto-aperture open is allowed.
The meter will direct read as you operate the aperture to brighten or dim the light coming throught the lens.
The meter itself is set to a default setting.
04-28-2012, 08:54 AM   #4
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thanks for the help. I tried this, using the lens in manual aperture and the meter did move slightly, but it is not consistent. I stopped down the lens then opened it up and the meter moved, but the next time I tried it did not. It seems this is going to be a pain to shoot macro if it is not metering on demand.

I dont quite understand this 'only the auto-aperture open is allowed'

04-28-2012, 09:25 AM   #5
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The auto tubes allow for auto diaphragm action but not auto exposure. The diaphragm will be stopped down automatically to the shooting aperture like a regular lens but the metering has to be done manually. There are some Asahi bodies that will not meter even when done manually. I have 3 bodies and one refuses to meter with tubes. I have to meter without tubes, then estimate the exposure, given the amount of extension. It's easier to just grab one of my other bodies for macro work.

Last edited by desertscape; 04-28-2012 at 09:32 AM.
04-28-2012, 01:57 PM   #6
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I have the extension tube operating manual. Here is what it says:

"The 6x7 Auto Extension Tube is designed for use with Takumar/6x7 interchangeable lenses from 55mm to 300mm. The Auto Extension Tubes can be use individually or in any combination, utilizing the fully automatic diaphragm of the lenses. For close-up data on each lens, refer to the Tables 1~6 (pages 2~9)."
The manual gives a procedure for how to use the close-up tables and determine exposure. In the tables are the various lenses with film-to-subject distance and an exposure factor. So I'd look for an on line manual.
04-28-2012, 08:32 PM   #7
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thanks guys, will try to utilise a polaroid back to help with exposure as well.
04-29-2012, 08:08 AM   #8
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...or you could have the body fixed so it does meter when the lens is in the manual mode.

04-29-2012, 10:27 PM   #9
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QuoteOriginally posted by desertscape Quote
...or you could have the body fixed so it does meter when the lens is in the manual mode.
that would be handy, can you give instructions on how to modify the body to do this? Would be much appreciated,
04-30-2012, 11:13 AM   #10
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Since the body you have is supposed to meter with tubes in the manual mode, it would be a fix, not a mod. I'm not sure how to fix it but I have long suspected the pin in the lens mount face may not be connecting correctly to the ext tube.
05-04-2012, 08:12 AM   #11
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looking at the tubes and body more carefully, the tubes which I have ( asahi pentax 6x7 tubes) dont actually let the meter know a body is attached.
I think i have fixed this by taping a small leaver on the underside of the meter. Now the meter knows a lens is attached and can meter while the lens is stopped down manually. Tape needs to be removed when a normal lens is attached.
Hopefully this is useful for other people too.



if anyone see any pitfalls with this please let me know before i break something
05-05-2012, 02:41 PM   #12
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Fabian: When a body is working correctly, the meter will be activated when an extension tube is attached to the body, even when there is no lens attached. This is done via the pin in the lens mount face. In defective bodies, connecting a tube to the body does not activate the meter, with or without a lens. Does your mod actually work?
05-06-2012, 03:24 AM   #13
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I can see a pin in pentax lenses which do catch onto the metering part in the mount. the tubes I have dont actually have anything to catch that pin and let the meter know something is attached.

Yeah the tape works, I think it just lets the meter know something is attached. Manual aperture metering is obviously required.
05-06-2012, 05:05 PM   #14
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I should have been more clear. The pin is on the lens mount face of the camera body. The tubes (and lenses) have a hole to accept the pin. The pin is spring loaded. This dual purpose pin locks the lens in place and activates the meter on most bodies.
05-06-2012, 09:51 PM   #15
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If the meter prism is working properly, when there is no lens mounted on the camera, or if there is a manual lens mounted on the camera, the feeler goes all the way to the side and tells the meter to work in stop down mode. If stop down metering doesn't work it is because something isn't timed properly or is damaged/broken. MOST IMPORTANT: remove the lens before removing the prism and re-install the prism before you put a lens back on. Not doing so can damage the system and require parts that are no longer available.
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