[JimJohnson]

Just received my Kenkos from ebay -- the ones that really do have contacts. The 12mm & the 20mm work flawlessly. The 36mm works as far as stopping the aperture down but it asks for focal length and reports the aperture as beginning with f/1.2, so that one must have a broken contact. Which pin would be the likely culprit?

EDIT: Never mind, contact cleaner did the trick.

Glad you got it to work, but if you suspected a missing contact, use my original post in this thread:
http://www.robertstech.com/matrix.htm

Answering your pre-edit question shouldn't take more than 5 minutes. You would:
#1- see what your camera said was the available aperture range
#2- use the chart in the supplied link to see what contacts are insulated to achieve that range
#3- examine your lens to see which contacts are supposed to be insulated
#4- comparing #2 & #3 would tell you which contact in your tube set was out of whack.

[vonBaloney]

Glad you got it to work, but if you suspected a missing contact, use my original post in this thread:
http://www.robertstech.com/matrix.htm

Answering your pre-edit question shouldn't take more than 5 minutes. You would:
#1- see what your camera said was the available aperture range
#2- use the chart in the supplied link to see what contacts are insulated to achieve that range
#3- examine your lens to see which contacts are supposed to be insulated
#4- comparing #2 & #3 would tell you which contact in your tube set was out of whack.

I am gonna study that stuff one of these days, I promise. Sounds like a super-useful mod. Thank you for sharing.

[mee]

I am gonna study that stuff one of these days, I promise. Sounds like a super-useful mod. Thank you for sharing.

Deep down you feel you wasted your money and your valuable time with these and want to sell them to me! :c )


I just know it!! now only if you would too! hehe

[vonBaloney]

Deep down you feel you wasted your money and your valuable time with these and want to sell them to me! :c )


I just know it!! now only if you would too! hehe

I wasn't going to pay a fortune for them, but there were no other bidders so it wasn't a problem. I'm might be willing to sell them for a fortune though, but not until I play with them a while. At some point I'm sure somebody will start producing some new ones and sell them for a reasonable price...

[mee]

I ended up buying a set of Vivitar AT-22 so I'll see how that goes.. most my lenses I want to use with this have aperture rings so shouldn't be a major issue.. I hope

[vonBaloney]

Ok, so still a bit of a mystery problem with my Sigma 70mm. I actually managed to pick up another set of these Kenko tubes, and they both only work (completely) intermittently with the Sigma 70 macro. That is, it will ask for focal length (if SR is turned on) and it doesn't know the aperture, although it is still able to set the aperture in live view (K-5) but lists it as starting from 1.2 rather than 2.8. (Top LCD shows F---) I figured it was the contacts on the tubes cause the contact cleaner seemed to do the trick, but I think that was just luck, and it turns out it is something to do with the lens instead. And these new set of tubes act just the same.

So, if I try the other AF & A lenses I have (which is only a few), they all work 100% of the time with the tubes except for my cheap Quantaray telephoto 70-300 zoom, which as luck would have it is actually also a Sigma. With that lens, it works most of the time, but if I wiggle it around I can get the contact to come and go. With the Sigma 70/2.8, it doesn't work most of the time, but does sometimes. With my few other A & AF lenses, contact is maintained 100% of the time no matter if I wiggle it like crazy. So what is with these Sigma lenses that they come in and out? I tried cleaning the contacts on the lens, no change. And the Sigma works flawlessly directly on the body. And also works flawlessly 100% of the time if I put it on my teleconverter with contacts. In fact, if I put lens->TC->tubes->body it works. Just on these tubes it has trouble.

Something not conducting properly, or not conductive enough? Sigma contacts don't have enough pressure on their springs? The mount groove is a little different? Can't figure out what is different about the Sigma. (Again, can't get a failure on my other lenses with these tubes no matter what.)

Thoughts? I'd like to get these tubes working with this lens reliably, and I'm going to sell one of these sets so I'd like to know where the blame is.

[JimJohnson]

Thoughts? I'd like to get these tubes working with this lens reliably, and I'm going to sell one of these sets so I'd like to know where the blame is.

Use the force Luke! Or go backwards a couple posts and spend a couple minutes to figure out which contact(s) are working and which are not. It's not rocket science to figure this out from the chart.

[baro-nite]

Something not conducting properly, or not conductive enough? Sigma contacts don't have enough pressure on their springs? The mount groove is a little different? Can't figure out what is different about the Sigma. (Again, can't get a failure on my other lenses with these tubes no matter what.)

I also have the Sigma 70/2.8 and have had similarly mixed success with A-type tubes. I don't have the answer, but note that DA-type lenses are missing two of the A-type contacts. Complete guess on my part but this might have an effect; I gather that 3rd-party manufacturers have had to reverse-engineer the mount and maybe there are some differences that become apparent when you stick a tube between camera and lens.

I have two more-or-less DA-type tubes (TCs). One of them has all 7 contacts. The other is missing one (just like the Kenko). The latter works correctly with the Sigma, the first does not transmit FL. Admittedly I haven't tried contact cleaner yet, but both tubes work correctly with Pentax-brand DA lenses. So there seems to be something different about the Sigma.

[vonBaloney]

Works perfectly on my 18-250, which is the only DA lens I have, and it has the exact same set of contacts as the Sigmas -- the aperture range is different though. I have a couple of manual-focus 'A' lenses (one of which is a Sigma) -- it gets the aperture right on those. If it failed 100% of the time, it would make sense that there was a missing contact or whatever. But it comes and goes as it is attached. The smallest tube seems to work most of the time, the biggest tube almost never works, and the middle tube is about 50-50. So it seems like some sort of conductivity issue. But even if I put all six tubes from both sets together with the TC between the tubes and the lens, all is good. Weird.

[mee]

I actually managed to pick up another set of these Kenko tubes...

huh? Where did you manage to find a second set?

[Jodokast96]

How heavy is that lens? I've had intermittent issues when using them with my 70-300, though mostly when using the full set. It seems that there's just a bit too much weight at the mount and there is just enough give to break contact with the contacts. I've had some success with switching the order of the tubes between the lens and body. But not total success.

[vonBaloney]

huh? Where did you manage to find a second set?

Locally.

How heavy is that lens? I've had intermittent issues when using them with my 70-300, though mostly when using the full set. It seems that there's just a bit too much weight at the mount and there is just enough give to break contact with the contacts. I've had some success with switching the order of the tubes between the lens and body. But not total success.

Both of the Sigmas are heavyish, but as I've been playing with this I've mostly been supporting them well. And as I wiggle them around, there really isn't much play, and the play that does exist is all rotational, not pulling down or outward pressure on the mount. And as the contact comes and goes, I can't consistently get it to work or not work by pushing, pulling, or rotating this way or that. It does sort of seem that it works a bit better the longer the camera is turned on like it takes a while for the electrons to get flowing, but that just may be my imagination. There isn't much rhyme or reason to it that I can tell. If there was it would probably point to a solution, or at least the cause of the problem. The only thing I can figure is the Sigma groove in the mount is slightly deeper or their contacts are made of a less conductive material or have weak springs or something (and maybe the Kenkos do too) -- some reason that just makes the tiniest bit difference to the connection on both sides that creates a bad match.

[vonBaloney]

Ok, making progress! I had the thought that maybe this wasn't a problem of something NOT being in contact, but a contact being made that shouldn't be. I also noticed that on my DA one of the unused pins actually has a non-conductive divot instead. So on the offending lenses, I put non-conductive tape in those two positions where they don't have pins (but the body mount/tube does). Well, this seems to have completely fixed the 70-300 zoom. Can't get it to fail now. And it has raised the success rate of the Sigma 70 by a great margin. It is still intermittent, but much less so. Still, if that was THE answer, seems like it would have just solved it period. But the improvement is significant, so I think I'm on the right track. Maybe just need better tape more precisely applied.

Anyway, something to try for you kids at home...

[Jodokast96]

I'll test it myself as soon as I get a chance. If I remember to, that is, lol.

[JimJohnson]

Ok, making progress! I had the thought that maybe this wasn't a problem of something NOT being in contact, but a contact being made that shouldn't be.

Folks, as much as I hate to be a nag, this is 100% in line with what I have been saying about checking out the chart mentioned in earlier threads in this post. You could have saved a LOT of head scratching time by looking up the contacts that match your lens' aperture range, then looking up the contacts for the aperture range your camera says it sees. Compare the two and you have your answer. Knowing what to fix is at least 3/4 of the way to fixing the problem.