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06-12-2018, 11:42 PM   #1
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extension tubes

I've seen that you can pick up 645 extension tubes on ebay such as the #3 39mm. I was wondering how they work with the 90mm macro - ie do they allow aperture control and AF and metadata pass-through?

Also what is the 'helicoidal' tube for?

06-13-2018, 12:21 AM   #2
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The genuine Pentax tubes do have lens data contacts (for aperture control), but focusing would be manual and SR may not be powered.

Not sure about third-party ones, but look for the contacts.

Adam
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06-13-2018, 01:24 AM   #3
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QuoteOriginally posted by Adam Quote
The genuine Pentax tubes do have lens data contacts (for aperture control), but focusing would be manual and SR may not be powered.

Not sure about third-party ones, but look for the contacts.
Thanks for the info Adam.
06-13-2018, 02:25 AM   #4
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QuoteOriginally posted by Adam Quote
The [URL="https://www.pentaxforums.com/accessoryreviews/pentax-645-auto-extension-tube-set.html"]......and SR may not be powered.
SR is lost with the tubes.

QuoteOriginally posted by Gyroscope Quote
Also what is the 'helicoidal' tube for?
Think of it as a variable length extension tube or mini-bellows....38-72mm but has no passthrough so everything is dumb.

Bob


Last edited by Bob L; 06-13-2018 at 02:32 AM.
06-13-2018, 12:42 PM   #5
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QuoteOriginally posted by Gyroscope Quote
Also what is the 'helicoidal' tube for?
It's a must for macro work and is also recommended for using a reverse adapter. You mount the helicoid tube to the camera body, then the reverse adapter and then the reversed lens. You can then adjust the magnification with the helicoid instead of having to move the camera/tripod.

I have the 6x7 helicoid and use it all the time doing 6x7 macro work, much easier to use than plain extension tubes.

Phil.
07-30-2018, 05:24 PM - 1 Like   #6
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QuoteOriginally posted by gofour3 Quote
It's a must for macro work and is also recommended for using a reverse adapter. You mount the helicoid tube to the camera body, then the reverse adapter and then the reversed lens. You can then adjust the magnification with the helicoid instead of having to move the camera/tripod.

I have the 6x7 helicoid and use it all the time doing 6x7 macro work, much easier to use than plain extension tubes.

Phil.
QuoteOriginally posted by gofour3 Quote
I have the 6x7 helicoid and use it all the time doing 6x7 macro work, much easier to use than plain extension tubes.
HI Gofour3
I already have the ext. tubes for shoting List item. I need more close-focus than Macro so the reverse adapter is useless for me.

But your comment stop me to buy the 6x7 Auto-Bellows for about $100, Thank you.

Now I find more convenience of getting the 6x7 Helicoid ($90) + Extensions tubes.

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