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08-08-2009, 07:20 PM   #1
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HELP! Extension tubes won't work

Hello:

Hope someone can help me out! I purchased the following set of extension tubes :

"Asahi Pentax Auto Extension Tube Set K-3 Ring K Mount " for my K10D. However, I could not get the shutter to release with a tube on. A "F" kept flashing, like when it does when I have the macro lens on and don't have it on the "A". Someone please tell me I can somehow make these work.....

Tks!

cdt

08-08-2009, 07:52 PM   #2
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Pentax extension tubes do not have data contacts. You have to treat the combination of extension tube + lens as a "manual" lens.

Read Me First - Using Manual Lenses with Pentax DSLRs

Note that to control the aperture of the combination, you need to use a lens with aperture ring NOT set at A.
08-09-2009, 05:01 PM   #3
ctt
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Thank you so much for replying!

I read your link, but of course am confused.

Just trying it out, I put the biggest extension tube on and dialed my macro lens to 5.6 apt. (my then focused and mashed the green button. 2" F-- comes up, but when I take picture, it's not even close to right exposure. What am I doing wrong??
08-09-2009, 05:21 PM   #4
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Might need a tripod and some flash

08-09-2009, 05:24 PM   #5
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QuoteOriginally posted by SOldBear Quote
. . .
Read Me First - Using Manual Lenses with Pentax DSLRs

Note that to control the aperture of the combination, you need to use a lens with aperture ring NOT set at A.

CTT,

Did you go into the menu and change the setting?
08-09-2009, 05:43 PM   #6
ctt
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Yes, just like u said!
08-09-2009, 05:43 PM   #7
ctt
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Would you be willing to talk to me on the phone?
08-09-2009, 06:37 PM   #8
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QuoteOriginally posted by ctt Quote
Just trying it out, I put the biggest extension tube on and dialed my macro lens to 5.6 apt. (my then focused and mashed the green button. 2" F-- comes up, but when I take picture, it's not even close to right exposure. What am I doing wrong??
You did nothing wrong, maybe except for trusting Pentax with lens compatibility

What camera body are you using? I assume it's one of the K-series....

What you experienced is a case of metering problem with manual lenses. This problem is well-known. Please do a search on this forum for many threads relating to this issue.

The smaller aperture settings, the more pronounced the problem.

With the extension tube and macro setting, the effective aperture is several times smaller than the setting on the lens. For example, even without extension tube, at 1:1 magnification, a setting of F/5.6 on my 55mm macro lens actually means F/11 (2X slower). With extension tube, F/5.6 setting may be actually as small as F/22 effective.

In my experience, at F/11 and smaller apertures, the metering error on a K10K can be 2X or 3X toward overexposure. So when the body set shutter speed at 2", the correct one can be 1/4".

The only solution to this metering problem that I know of (and have verified with both of my K10D bodies) is to replace the stock LI-80 focusing screen with an LI-60 or LL-60 screen (or any other -60 series). The -60 screens are the ones for *ist camera bodies.


Last edited by SOldBear; 08-09-2009 at 06:48 PM.
08-10-2009, 01:16 PM   #9
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QuoteOriginally posted by ctt Quote
However, I could not get the shutter to release with a tube on. A "F" kept flashing, like when it does when I have the macro lens on and don't have it on the "A". Someone please tell me I can somehow make these work.....
Have yoiu switched to manual focus? If the tubes do not have a screw or SDM contacts and you have the camera set to one of the AF modes, then the camera will not take a photo until it finds the centre in focus, and it won't be able to focus the lens...

Richard
08-11-2009, 04:36 PM   #10
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Yes, make sure you put the dial in "manual".
That was my mistake before as I left the dial to "Av".
Stop-down metering only works on manual setting.
This would still give you the F-- reading but the exposure would be right.
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