Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-13-2012, 11:53 AM   #61
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
QuoteOriginally posted by JimJohnson Quote
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.
Yes and no. We are now talking about blocking contacts that aren't even there. Shouldn't have to do that. (And it still doesn't work all the time -- yet.) I am looking at that chart though. My old Sigma Super-Wide II manual focus has suddenly decided it is an f/4 lens instead of an f/2.8 lens, even without the tubes. Gotta figure out what is going on there...

06-14-2012, 11:24 PM   #62
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
Sorry Jim, the contact positions don't seem to be a help here -- I don't think these AF lenses are even using those at all (in that way). Putting tape in the spots where there are no pins on the lens does seem to be a big improvement in reliability (but not 100% reliability), but I don't know why. It doesn't seem to be because it is causing the right 1/0 pattern as according to the matrix chart. I'm putting tape over positions that should be 1's and a few of the 0 spots actually have pins on the lens mount. If I block those, the lens won't work period -- tubes or no tubes. So it seems these newer AF lenses are using a completely different communication system involving the data pin and probably other pins, in a less "dumb" way then just shorting/not shorting.

My manual focus 'A' lenses have insulators on them and conform to the chart -- those work fine already. But these AF lenses all have the exact same set of pins, which are (according to the matrix chart): D 1 2 A 5. No pins 3 or 4. On my DA 18-250, position 3 has divot pin hole with a plastic insulator, and pin 4 is bare metal mount. On the Sigma 70/2.8 and Sigma zoom, both 3&4 are bare metal. These are the positions I've putting tape on that are helping -- seems to fix the zoom completely, and the 70 is more reliable but still erratic. I've also tried blocking each position individually -- I think the 3 position may be the key one.

So -- it all comes down to flaky connections? The big tubes are the least reliable, and the more tubes used total the less reliable it is. So the tubes just aren't using the greatest materials for pin conductivity? If so, I'd expect same flakiness with all lenses -- the 18-250 works great 100% of the time (if only I wanted to actually use the tubes with this lens). Unexplained also is how taping off the bare metal portions makes it work better (since it doesn't seem to conform the matrix pattern -- thought maybe it was "falling back" to that if data connection was failing, but the patterns just don't match, and how do those work on a zoom lens with changing aperture ranges anyway?). So the Sigma is also using substandard materials in its mount, that along with the tubes create intermittent failure? Seems dubious. (TC works great with Sigma, and also improves reliability if put between tubes and lens.) Maybe there is a certain pin that is used by the Sigma that is not used by others? That's possible (it is a 2.8 lens and the other two AF lenses are slow zooms.), but still unlikely as the culprit -- each individual tube has failed alone at one time or another with the Sigma -- they can't all be broken. My Sigma is just bad? Unlikely also -- others report same thing, and it works fine on TC or on body. And again, why does the tape help? Decreases interference?

So, back to square one, sort of. A bit of tape helps, but doesn't totally solve the problem. In practice, in nearly solves it, because you won't be wiggling the tubes all around as I am in testing. And even when it is in "not working" mode -- it still works, sort of. It *will* stop down the aperture -- you need live mode to see changing numbers though (the wrong numbers), as the others just display "F--" even as the meter still operates (the shutter speed will change), but will report incorrect aperture numbers. So you can actually count clicks to set aperture without live mode or just figure the offset in live mode where it does display an aperture number (the wrong number). Using live mode on a flaky connection is hard though, because live mode immediately shuts off if changes from fully working->partially working or vice-versa.

Seems like there is still a simple solution lurking, or at least a sensible explanation. Can't find it.

To those of you also experiencing flakiness with 'A' tubes -- what brand are they? Kenkos, like these? (Kenko Uniplus tube, anyone?) Could I expect a set of Vivitar AT-23s (or Jessops) to be more reliable? Anyway, still gonna sell one of these sets of tubes, and am still going to attempt to get a healthy price for them. They don't seem to be "broken" since both sets act the same and everybody else reports similar weirdness. I was hoping to have a good explanation or solution before I pass them but I will just have to warn buyers of potential issues with some lenses so they can buy them with eyes open.

Last edited by vonBaloney; 06-14-2012 at 11:30 PM.
06-15-2012, 03:05 AM   #63
Veteran Member
Louicio's Avatar

Join Date: Mar 2012
Location: Melbourne
Posts: 432
QuoteOriginally posted by wowtip Quote
Can you find these anywhere? Looked at the bay and elsewhere, but no luck. Preferably something in the 20 - 30mm range, or more.
There are a set of Kenko ones now in the marketplace.
https://www.pentaxforums.com/forums/photographic-equipment-sale/189496-sale-k...-contacts.html
06-15-2012, 03:10 AM   #64
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
QuoteOriginally posted by Louicio Quote
Yeah, those are mine -- one of the sets I've been talking about.

06-15-2012, 05:30 AM   #65
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,365
QuoteOriginally posted by vonBaloney Quote
Sorry Jim, the contact positions don't seem to be a help here -- On the Sigma 70/2.8 and Sigma zoom, both 3&4 are bare metal. Seems like there is still a simple solution lurking, or at least a sensible explanation. Can't find it.
After 30+ years of providing computer tech support, I've learned the hard way to not assume anything ... so, I'm not not trying to insult you, but have to ask, are you applying your insulation spots at the body end of the tube? If there is something going on inside the tubes (obviously, since the lens works fine when directly connected) we need to isolate the tubes from the camera body.

I also suspect you are correct that the Sigma lens is making use of the data pin. That pin sends variable signals, not just an on or off like the rest of the pins. If I can make the following suggestion? Let's force the lens to work like your older and completely mechanical 'A' lens and avoid the lens' electronics. Let's start with the 70/2.8. I am guessing that your aperture range on this lens is f/2.8 - f/22? If so, on an 'A' series lens there would be no data pin, nor pins 1 or 5 (using robertstech's numbering sequence). So let's try insulating those 3 contact points between the camera body and whichever tube you mount to the body. And, make SURE that the 'A' , 2, 3, and 4 pins ARE shorted at the body.

At this point, it won't matter what lens you put on your camera. It will assume the lens is in the 'A' position and capable of an aperture range of f/2.8 - f/22. When you turn the camera on, you will need to tell it you have a 70mm lens.

After setting an aperture on your camera body and manually focus, when you release the shutter, the body's aperture linkage wil move the correct portion of its travel for the designated aperture. The springs in the lens will pull the aperture closed until the combined tube/lens aperture linkage hits the stop created by the body's aperture linkage. The lens' aperture should match the body's selected aperture. Mechanically this should all happen during the time the mirror gets out of the way of the shutter/sensor.

I appreciate you taking a look at the chart. You have spent this much time already on this project. Will you spend the few more minutes to give the above a try?
06-15-2012, 09:14 AM   #66
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
QuoteOriginally posted by JimJohnson Quote
After 30+ years of providing computer tech support, I've learned the hard way to not assume anything ... so, I'm not not trying to insult you, but have to ask, are you applying your insulation spots at the body end of the tube? If there is something going on inside the tubes (obviously, since the lens works fine when directly connected) we need to isolate the tubes from the camera body.
Not to the tubes at all. To the lens. I'm just covering up the bare metal in those spots where there are no pins.

QuoteQuote:
I also suspect you are correct that the Sigma lens is making use of the data pin. That pin sends variable signals, not just an on or off like the rest of the pins. If I can make the following suggestion? Let's force the lens to work like your older and completely mechanical 'A' lens and avoid the lens' electronics. Let's start with the 70/2.8. I am guessing that your aperture range on this lens is f/2.8 - f/22? If so, on an 'A' series lens there would be no data pin, nor pins 1 or 5 (using robertstech's numbering sequence). So let's try insulating those 3 contact points between the camera body and whichever tube you mount to the body. And, make SURE that the 'A' , 2, 3, and 4 pins ARE shorted at the body.

At this point, it won't matter what lens you put on your camera. It will assume the lens is in the 'A' position and capable of an aperture range of f/2.8 - f/22. When you turn the camera on, you will need to tell it you have a 70mm lens.

After setting an aperture on your camera body and manually focus, when you release the shutter, the body's aperture linkage wil move the correct portion of its travel for the designated aperture. The springs in the lens will pull the aperture closed until the combined tube/lens aperture linkage hits the stop created by the body's aperture linkage. The lens' aperture should match the body's selected aperture. Mechanically this should all happen during the time the mirror gets out of the way of the shutter/sensor.

I appreciate you taking a look at the chart. You have spent this much time already on this project. Will you spend the few more minutes to give the above a try?
Yes, I could cover up the entire lens mount of the Sigma including contacts with foil tape (making it a blank slate) and then insulate the correct spots and it would probably work in the way that you state. I have no reason to think otherwise -- I've already got a manual focus A lens with the same aperture range that works fine. But all we would prove is that the matrix chart is correct, and 'A' lenses work in a certain way, etc. We've essentially taken the tubes out of the equation and we could do the same thing with non-'A' tubes as you yourself have done. But remember, this is an AF lens that I also want to use sans tubes, and I want to be able to pop them on and off and use the lens normally of the body (which means AF, which I presume wouldn't work with our dumbed-down version of the contacts).

So, while that would be an answer to using this particular lens with macro tubes, it doesn't solve our mystery of why it won't work as it is supposed to in the first place -- remember these tubes are marketed for AF lenses, not just A -- nor does it actually get things working as they are supposed to, but is a "simulation" if you will of working correctly by using a completely different route to get there. And then I've got a "dumb" lens that I can't use normally (with AF) when I take the tubes off without fussing with a bunch of tape each time, or if I insulate the tubes instead of the lens then I can't use them with other lenses (quickly). It all defeats the whole purpose of having the contacts in the first place which is to have it all "just work" without hassle. And again, when these are "not working", it is more of an annoyance that a huge problem, I am losing the display of the number but I can in fact still stop down with the body and meter, etc.

I do have another set of tubes on the way -- non-contact tubes but that have mechanical linkages -- these cost basically nothing and it would make more sense to insulate those permanently to use only with this particular lens (or others with same aperture range) if I modify the A pin on the camera body as you suggest. (Of course, then I've got to carry them too.)

One question I have. On the manual focus 'A' lenses, there is an 8th pin -- which is also duplicated on these tubes but not on my TC with contacts (which also passes through AF drive). If the data pin is 0, this pin would be in the -3 position (usually there is a screw in-between the other 7 pins and this plus some empty space). I don't see this pin mentioned on these sites that talk about the mount. It isn't on the AF lenses. Is it actually the Ricoh pin, I wonder? The A lenses I'm looking at are third-party, I don't have any Pentax-branded As (manual) at the moment. I tried blocking it off for the hell of it -- no effect.

Last edited by vonBaloney; 06-15-2012 at 09:47 AM.
06-15-2012, 11:47 AM   #67
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,365
Oh oh ... you got the right ideas, but you have the wrong end of the stick - or in this case the wrong end of the extension tubes. Your lens is fine. We know it is fine because it works normally when connected directly to the camera body. Your problem is is how your lens is being interpreted by the body when attached to the extension tubes. You need to stop trying to make your changes at the lens/tube interface and make them at the body/tube interface. If for no other reason, as you point out, you do still want to connect the lens directly to the body and retain full functionality. And other than stuffing the 'A' contact on the camera body, you likewise don't want to be placing and popping pieces of tape on your body - so do your work at the body end of your most often used tube.

I am looking at 3 side by side SMC Pentax-A lens (28mm, 50mm and 70-210 zoom). None of these lens have anything like an 8th pin. Other than the standard 7 contact points and screws you note, the only other item on the lens mount flange is the hole for the mounting lock. I am pretty sure you are not referring to that. And I just looked at my K-r body... no sign of an 8th contact position there either, unless you are looking at the screw drive for AF? Is there any sort of matching 8th contact point on your Sigma lens?

I'm starting to wonder if your tubes were intended for use on one of the non-Pentax K-mount systems?

For what it's worth, after I rigged my macro adapter specifically for my 50/1.7 prime lens, I mounted my DA L 50-200 lens on the adapter, and set the lens at 50mm. So the only difference was the new lens had a different aperture range and no aperture ring.

Because I did not change my insulation patch on the body end of the macro adapter, the aperture range shown in the camera was now incorrect for the mounted lens (and therefore the exposure was off by about a half stop or less). If i wanted to do so, it would take me maybe 10 minutes to swap the insulation patches to match the new lens' aperture range.

The DA series lens otherwise worked just fine with the camera body controlling everything but AF. Remove the lens and adapter from the camera and mount just the DA lens for full functionality, including AF. The point is, while I plan to use this adapter only with my 50mm prime, like you I also want to be able to just mount a lens directly to the camera without fuss and with full functionality.

I'll let you reach your own conclusions about paying for extension tubes with contact points that don't seem to work out of the box with the lens you want to use them with.
06-15-2012, 11:50 AM   #68
Inactive Account




Join Date: Jul 2008
Location: South Africa
Posts: 62
I have a Sigma 50-500 and a set of Jessops extension rings with the seven electrical contacts. Reading all the above comments I tried them out with the Sigma and with the K5 set to Av mode there was no F stop reading as I expected.
I then ran a wire from the chrome lens base plate to the chrome camera lens mount and the F stop reading worked perfectly.
If you examine the electrical continuity of the Jessop extension tubes you will see that there is no electrical path between the base of the lens and the camera body. I’m not talking the pin path here but more like an earth.
Could someone please check this out and debunk or confirm my understanding.
Greg

06-15-2012, 12:07 PM   #69
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
QuoteOriginally posted by JimJohnson Quote
Oh oh ... you got the right ideas, but you have the wrong end of the stick - or in this case the wrong end of the extension tubes. Your lens is fine. We know it is fine because it works normally when connected directly to the camera body. Your problem is is how your lens is being interpreted by the body when attached to the extension tubes. You need to stop trying to make your changes at the lens/tube interface and make them at the body/tube interface. If for no other reason, as you point out, you do still want to connect the lens directly to the body and retain full functionality. And other than stuffing the 'A' contact on the camera body, you likewise don't want to be placing and popping pieces of tape on your body - so do your work at the body end of your most often used tube.
If I make them there, it much harder because I have to cover up existing spring-loaded pins (tends to shed the tape), and presumably ruins them for use on other lenses without more fussing with tape or whatever. In short, it is a solution, but it isn't worth it. Putting tape on the lens itself in the empty spots fixes it MOST OF THE TIME and completely fixed it on the the other Sigma lens. I wish I had more to test. So I'm going to be annoyed either way -- I choose lens side for now.

QuoteOriginally posted by JimJohnson Quote
I am looking at 3 side by side SMC Pentax-A lens (28mm, 50mm and 70-210 zoom). None of these lens have anything like an 8th pin. Other than the standard 7 contact points and screws you note, the only other item on the lens mount flange is the hole for the mounting lock. I am pretty sure you are not referring to that. And I just looked at my K-r body... no sign of an 8th contact position there either, unless you are looking at the screw drive for AF? Is there any sort of matching 8th contact point on your Sigma lens?

I'm starting to wonder if your tubes were intended for use on one of the non-Pentax K-mount systems?
No, its a pin/contact. Gotta be the Ricoh pin, a contact button in this case like the rest. No matching pin on the body, its for Ricoh cameras. I've had them on other lenses, now sold, but those were always marked for Pentax and Ricoh. I think they're standard on many third-party A lenses. Pentax-A's don't have them, as I suspected (they wanted you to buy Pentax, not Ricoh). The second set of tubes I bought -- which are exactly the same -- came in the box with instructions and they clearly say Pentax AF. They also say "for digital" -- they just put some "DG" stickers on them but they are exactly the same.

QuoteQuote:
I'll let you reach your own conclusions about paying for extension tubes with contact points that don't seem to work out of the box with the lens you want to use them with.
Well, the main reason I was trying so tenaciously to find an *easy* solution is so I can sell them to somebody else and have them know what they are getting, possible issues, and what to do about it. We've succeeded part way on that score, but if everyone else is experiencing the same thing and at least I've found an improvement and you've posted a possible alternative (I've linked to this thread from my sales thread, which has pics of the tubes btw), I have to throw up my hands at some point, and my conscience is clear. It is just an annoyance after all and not something that will prevent someone from "getting the shot", which is the important thing.

For myself, if I find that I am too annoyed when trying to get those shots, maybe I'll try a different solution. Probably wait until those dumb tubes get here. But having the ones with contacts that DO work on most lenses is mighty nice and makes it convenient to throw them on any lens at any time to get closer. They are still worth it.
06-15-2012, 12:55 PM   #70
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,365
QuoteOriginally posted by gregmoll Quote
you will see that there is no electrical path between the base of the lens and the camera body. Iím not talking the pin path here but more like an earth.
Good heavens! That possibility never even dawned on me! I know the contact pins are only half the circuit and the body flange is the other half. WHY would ANYONE manufacture something with the mechanical complexity of all those spring-loaded contact points and not provide for a COMPLETE electric cicuit? That just boggles my mind!
06-15-2012, 01:11 PM   #71
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
QuoteOriginally posted by gregmoll Quote
I have a Sigma 50-500 and a set of Jessops extension rings with the seven electrical contacts. Reading all the above comments I tried them out with the Sigma and with the K5 set to Av mode there was no F stop reading as I expected.
I then ran a wire from the chrome lens base plate to the chrome camera lens mount and the F stop reading worked perfectly.
If you examine the electrical continuity of the Jessop extension tubes you will see that there is no electrical path between the base of the lens and the camera body. I’m not talking the pin path here but more like an earth.
Could someone please check this out and debunk or confirm my understanding.
Greg
The Kenko tubes do have black presumably non-conductive material on the "lens side" (the side the pretends to be a lens) and chrome metal on the body side (the side the actual lens mounts to). See pics in my sales thread. But since all pins are represented I figured this didn't matter. So you think if both sides were conductive it would work, or I guess it might still need a wire? The thing that gets me is that it both works and doesn't work intermittently, and of course it works great with many lenses. All of these theories would seem to indicate that it should either never work or always work -- i.e. if that connection is necessary and it is not there, then why doesn't it simply NEVER work? That would make sense, and the solution would also be clear. But since it does seem to come and go, even when you think you've found the answer you have to really give it a good test because it could just be working at that moment because of luck -- like I originally thought after using contact cleaner. Didn't work, cleaned it, then it worked. I thought problem solved, but not so fast...

EDIT: You know, the pin I'm calling the Ricoh pin actually does provide a path through -- you can see both ends of it touch in the middle when you press the pin from both sides, which is what I assume all the pins do (but they are hidden internally). And it is not represented on the body so it does provide a path from the bare metal of the body mount to the bare metal of the lens mount.

Last edited by vonBaloney; 06-15-2012 at 01:21 PM.
06-15-2012, 01:34 PM   #72
Inactive Account




Join Date: Jul 2008
Location: South Africa
Posts: 62
The Jessops tubes do not have the Richo pin to act as an earth path. None of my FA lenses work in Av mode.

Anyway I've stripped the first tube ready to sand off all the annodising tomorrow morning.
Greg
06-15-2012, 01:37 PM   #73
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
QuoteOriginally posted by gregmoll Quote
The Jessops tubes do not have the Richo pin to act as an earth path. None of my FA lenses work in Av mode.

Anyway I've stripped the first tube ready to sand off all the annodising tomorrow morning.
Greg
Score one for the Kenkos for at least trying? I will investigate this path...
06-15-2012, 02:25 PM   #74
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,393
Ok, we may have found our answer. Even though the Kenkos do provide that path, assuming it is not good enough I added foil tape next to it on each tube wrapping from the mount on one side around the exterior of the tube to the mount on the other side, providing an additional grounding path. I didn't want to start putting things on the set I'm selling, so on the other set I just wrapped a piece of tin foil around the mounts the same way. So now I've got six tubes all connected at once -- a sure path to failure. I took the tape off the Sigma lens (that was blocking the contacts). So with the foil, it does work much better, but again not foolproof. So I put the tape back on the lens blocking the missing pins, and that does seem to be foolproof. So for some reason this lens is having something get shorted that shouldn't be in one or both of those spots AND it needs a more reliable grounding path. Nevertheless, VICTORY!

So it sounds like the smart play would just be to remove the black from the black side, or at least some of it away from the pins. Do you think that would be good enough to provide grounding path, or a wire or foil is actually needed to connect the sides? An internal connection could be added (or the Ricoh pin connection could be "shored up") to make it prettier. The foil tape is easy enough I guess, but then I still need the bits of blocking tape for total reliability, which I still find weird. Kludgy, but it works!

Last edited by vonBaloney; 06-15-2012 at 02:36 PM.
06-15-2012, 05:54 PM   #75
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,365
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.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
tripod
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to use extension tubes? chinotenshi Troubleshooting and Beginner Help 15 12-18-2010 06:26 AM
Extension tubes Gary G Pentax DSLR Discussion 2 04-14-2010 06:28 PM
extension tubes keithbaran Troubleshooting and Beginner Help 15 02-25-2010 10:48 PM
Extension tubes axl Photographic Technique 9 12-19-2008 03:31 PM
Extension Tubes kpfeifle Pentax Camera and Field Accessories 2 02-29-2008 12:24 PM



All times are GMT -7. The time now is 12:41 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top