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06-15-2012, 06:26 PM   #76
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QuoteOriginally posted by JimJohnson Quote
vonBaloney - do you own a VOM (volt, ohm meter)? Most hardware stores sell them for under $20 and they have a lot of uses around the house. The function I have in mind is a continuity (beep) test. Without the camera or the lens attached to the tubes, touch one lead to a spot on the bare metal mount, then touch the other lead in turn to the other mount (including the underside edge of the male mounting prongs) and to each of the contact pins - especially that mysterious 8th pin. Any time you make a circuit, the meter will beep. I am beginning to wonder if that unusual contact pin isn't in fact a grounding pin. As previously noted, grounding typically happens through the mating of the male and female bayonet mounts ... but maybe with your set???

The meter could also quickly allow you to determine if each tube's contacts are solid when multiple tubes are joined.
I do not have a meter, unfortunately. I do not think that 8th pin is supposed to be a grounding pin -- it is supposed to be whatever it is -- the Ricoh pin. Could be for flash or something -- I don't know. Like I said, that pin actually exists on the manual focus A lenses I have. (Which all work fine.) I suspect that 8th pin provides a grounding path only accidentally -- which could explain why it sucks at it. What doesn't make sense is why they would market tubes for "Pentax AF" (even "for digital" on my second set) and not provide the correct contacts. Or maybe Sigma is just cutting corners with something -- the tubes do work with my AF aperture-ringless DA 18-250 flawlessly with no mods needed, after all. So I think this is all caused by some lenses needing that path for whatever reason, but I'm guessing official specs would not require such a path. But maybe not, with others saying their FA lenses don't work. I'm just happy to have found a solution. If I ever get a hold of a voltmeter I'll test it out though.

06-16-2012, 04:26 AM   #77
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I have now fixed my Jessops Ext Tubes, The first one I did the long way round by dismantling it completely and sanding away all the anodising on the mating surfaces, never again. The other two were done as per the photos posted here. Everything works perfectly now.

How Jessops ever sold this item I don't know.

BTW my tubes have seven electrical contacts, I've seen Jessop Tubes with six contacts

Greg
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06-29-2012, 07:00 PM   #78
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I recently got some "black" no-contacts Jessops tubes too, and after trying them for a bit in fully manual/stop down metering had been thinking about trying to "fake" them to be a bit more modern-lens-like by connecting pins... And here I find someone had already done it.
A little firmware addition would mean all this would be unnecessary. As well as inputting focal length for shake reduction purposes when using older/non-auto-connected lenses, the aperture range could be set too.
I think further fairly simple firmware changes could make older lenses etc. much more user-friendly, but that's another topic really...
06-29-2012, 07:32 PM   #79
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QuoteOriginally posted by Moo Quote
I recently got some "black" no-contacts Jessops tubes too, and after trying them for a bit in fully manual/stop down metering had been thinking about trying to "fake" them to be a bit more modern-lens-like by connecting pins... And here I find someone had already done it.
A little firmware addition would mean all this would be unnecessary. As well as inputting focal length for shake reduction purposes when using older/non-auto-connected lenses, the aperture range could be set too.
I think further fairly simple firmware changes could make older lenses etc. much more user-friendly, but that's another topic really...
Couple of notes: shake reduction goes out the window once you start adding tubes and teleconverters -- in other words the correct value to input would no longer be the true value of the lens. Also M & A lenses use the mechanical linkage differently, so if using an M style lens if you fake it to make it think it is an A, it actually won't set the aperture correctly. Seems like the "fake A" think would work best with m42s where you are stopping down manually.

06-29-2012, 09:06 PM   #80
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QuoteOriginally posted by gregmoll Quote
BTW my tubes have seven electrical contacts, I've seen Jessop Tubes with six contacts
Unless a tube also supports AF, six contacts is better than seven.

Why? I don't remember. I'll have to dig up my notes and report back.
06-29-2012, 10:17 PM   #81
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QuoteOriginally posted by SOldBear Quote
Unless a tube also supports AF, six contacts is better than seven.

Why? I don't remember. I'll have to dig up my notes and report back.
Please do -- could relate to the weirdness we're getting with some AF lenses (since the tubes don't actually support AF, but they are supposed to support AF lenses).
06-29-2012, 11:14 PM   #82
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QuoteOriginally posted by SOldBear Quote
Unless a tube also supports AF, six contacts is better than seven.

Why? I don't remember. I'll have to dig up my notes and report back.
The test is with a K-7 body and these two tubes:



Both tubes have anodized (black) on the surface mating with the camera. On the 6-pin tube, at pin 7 position, the surface has been sanded to bare metal.

The 6-pin tube (right, actually a gutted 2X TC) works fine with any lens. Of course there's no AF.

The 7-pin tube has these problems:
  1. With SDM lenses (DA* 16-50 and DA* 50-135), focus confirmation and focus-trap don't work. When the camera is set at AF-S, the camera does not take photo because it thinks focus has not been achieved. When the camera is set at AF-C or MF, the camera takes photo regardless whether focus has been achieved.
  2. With screw-AF lenses (DA 40, DA 70, and Sigma 50 macro), the camera thinks the lens + tube combo is screw-AF and tries to focus (of course to no avail). The grinding noise of the camera's AF motor is loud and annoying.

When I use a piece of Al foil between the tube and the lens to ground pin 7 (at 12 o'clock position of the tube on the left in photo above), those two problems go away.

Last edited by SOldBear; 06-29-2012 at 11:22 PM.
06-30-2012, 02:50 AM   #83
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Thanks, my K5 and the 7 pin Jessop ext tubes behave exactly the same.

I'm now thinking of grounding the 7th pin permanently, do you foresee any problems.

Greg

08-14-2012, 03:38 PM   #84
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Come across these "Firstcall Extension Tube Set DG Pentax Set"
advertised as AF and has all the contacts , has anyone heard or had any experience using them?
Firstcall Extension Tube Set DG Pentax Set of 3

08-14-2012, 04:30 PM   #85
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QuoteOriginally posted by Malfunction Quote
Come across these "Firstcall Extension Tube Set DG Pentax Set"
advertised as AF and has all the contacts , has anyone heard or had any experience using them?
Firstcall Extension Tube Set DG Pentax Set of 3
The picture looks like they are for Canon. Actually, I see they are using the same pic for all brands. Best to ask about them and try to get an actual pic before buying...
08-14-2012, 04:33 PM   #86
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QuoteOriginally posted by vonBaloney Quote
The picture looks like they are for Canon...
It says for Pentax ,the site probably uses the same photo for all mounts .

Just checked and they do use the same photo for all the mounts the tubes come in.
http://www.firstcall-photographic.co.uk/search/Firstcall+Extension+Tube+Set+DG

Last edited by Malfunction; 08-14-2012 at 04:37 PM. Reason: correction
08-14-2012, 05:54 PM   #87
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QuoteOriginally posted by Malfunction Quote
Come across these "Firstcall Extension Tube Set DG Pentax Set"
advertised as AF and has all the contacts , has anyone heard or had any experience using them?
Firstcall Extension Tube Set DG Pentax Set of 3
The Firstcall set is actually the same set sold under the Kenko lable. Few places have them in stock in the U.S. and they go for US$199.00. It looks like most of the hits on Google are vendors in the UK.
08-14-2012, 05:59 PM   #88
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I bought a JC Penney Auto 2X TC for $20 and removed the glass, creating a 25mm A tube. It's a great and inexpensive way to get auto tubes IMO.
Two more cheap KA extension tubes.: Pentax SLR Talk Forum: Digital Photography Review
08-14-2012, 06:12 PM   #89
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QuoteOriginally posted by audiobomber Quote
I bought a JC Penney Auto 2X TC for $20 and removed the glass, creating a 25mm A tube. It's a great and inexpensive way to get auto tubes IMO.
Two more cheap KA extension tubes.: Pentax SLR Talk Forum: Digital Photography Review
Correction- It's a great way to get a 25mm tube. If all you want/need for extension is a multiple of 25mm and A-series support, it's not a bad way to go. However, if you want to extend a DA lens, you are out of luck; or if you want something other than a multiple of 25mm, it can be more difficult/expensive finding the lower and higher power teleconverters to get the other tube lengths.
08-14-2012, 06:17 PM   #90
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QuoteOriginally posted by JimJohnson Quote
However, if you want to extend a DA lens, you are out of luck.
Why are you out of luck with a DA lens? If it has contacts, then you control the aperture with the body as usual. And the TC version has the advantage of actually having AF gear-drive pass-thru (on some of them), which I don't think any of the dedicated tubes have.
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