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03-04-2022, 05:51 PM   #1
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Are there any D FA compatible extension tubes

I know Pentax has never made any, does any make or ever made any with the electric hookups?

03-04-2022, 06:58 PM   #2
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I believe it is Kenko that made the Pz AF Uniplus extension tubes in K mount, I suspect they were made decades ago and have long since been discontinued They are said to be rather rare and difficult to find. I have only been able to find a 25mm version, however it has all the electrical contacts required for use with D-FA lenses.


Last edited by Digitalis; 03-04-2022 at 07:33 PM.
03-04-2022, 09:11 PM   #3
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As well as the Kenko extension tube mentioned by Digitalis, there are also Kenko teleconverters that have all the contacts and mechanical links for autofocus and lens control. If you take out the lens elements (a very simple, straight-forward job), you can use the remaining hull as an extension tube. There are several sizes (2X and 1.4X and what Kenko calls MC4 and MC7 versions) that would give you several possible extension tube lengths.

I don't know how the prices compare to the genuine extension tube, but there are any number of them out there on Ebay.
03-04-2022, 11:45 PM   #4
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something to look for. I have no idea why no one at Pentax ever got around to making these themselves.

03-05-2022, 12:31 AM   #5
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QuoteOriginally posted by dkpentax Quote
I have no idea why no one at Pentax ever got around to making these themselves.
I myself am perplexed over this as well. Surely a simple extension tube would be relatively more straightforward to make than a specialized and expensive macro lens that may/may not suit everyone's needs, extension tubes give you quite a bit of flexibility.
03-05-2022, 01:08 AM   #6
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QuoteOriginally posted by AstroDave Quote
As well as the Kenko extension tube mentioned by Digitalis, there are also Kenko teleconverters that have all the contacts and mechanical links for autofocus and lens control. If you take out the lens elements (a very simple, straight-forward job), you can use the remaining hull as an extension tube. There are several sizes (2X and 1.4X and what Kenko calls MC4 and MC7 versions) that would give you several possible extension tube lengths.

I don't know how the prices compare to the genuine extension tube, but there are any number of them out there on Ebay.
Good idea too. Maybe a TC comes along with a damaged or dusty lens that sells cheap. I have a Kenko myself and it works quite well (as a TC).

Note that these may come in other brands, so examine TCs carefully for their potential as extension tubes with full electrical contacts.
QuoteQuote:
The Kenko 1.5x Teleplus, the Promaster Spectrum7 AF 1.7x, the Vivitar Series 1 1.4x, and the Tamron-F 1.4X Pz_AF
and perhaps other rebranded models...
03-05-2022, 07:56 AM   #7
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If manual focus is ok there are a few more options. I have a set of Hansa PK/A tubes. They preserve the A series level functions for non KAF4 lenses (anything with an aperture lever) but these are also rare.

The extension tube I converted was more constricted than these tubes. The opening is narrower than Iíd like. Iím unclear if this impacts exposure as moving the lens magnify the image circle and I havenít seen any vignetting but I also havenít worked at it very hard.

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03-05-2022, 03:45 PM   #8
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A word of caution, some of the tubes with the "a" contacts have AF in their name but this doesn't mean auto focus. I suspect it refers to the aperture function. I have a set of these which are Teleplus branding.
I also suspect that at macro distances AF is unreliable.
03-06-2022, 10:35 PM   #9
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QuoteOriginally posted by AstroDave Quote
here are also Kenko teleconverters that have all the contacts and mechanical links for autofocus and lens control. If you take out the lens elements (a very simple, straight-forward job), you can use the remaining hull as an extension tube.
Most TC's are still pretty thick so I don't think there is much to be gained by doing this.





Also the Kenko extension tube has a plastic inner component in the middle of it :


This ring has no detectable impact upon vignetting, but I have seen instances of this part of the tube getting scorched or melted due to sunlight being focused upon it - something to be wary of with all lens accessorizes.


Also the price of automatic extension tubes* from the official Pentax (Australia) website are extortionately expensive. I paid $100 Australian for a full boxed set in mint condition.





*Note: these don't have passthrough contacts for AF or AE.

Last edited by Digitalis; 03-06-2022 at 10:42 PM.
03-07-2022, 05:48 PM   #10
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I haven't tried any tests, but I am wondering if extension tubes actually work with modern internal focus lenses, where the rear element thinks its fixed compared to the image plane. old lenses of course just moved the whole lens in and out.
03-07-2022, 08:04 PM   #11
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did a quick test to tubes on a fa 400 5.6, and I see no visual issues that are obvious about it apart from the light falloff which is normal.
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