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Pentax PKA-AF Extension Tube problem

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February 9, 2005 1:37:30 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Hi all,
Can onyone help me resolve this problem please? I have a set of PKA-AF fit
extension tubes (Jessop branded) which seem to have the necessary electrical
contacts passing through them to suit A-Series lenses and the *istDS. If I
fit my old standard Pentax-A 50mm f1.7 PKA lens directly to my *istDS the
lens works as expected with the aperture ring set to 'A'. If I then place
any or all of these tubes between the camera and lens the Av indicator on
the camera shows only -.- and obviously reduces the capability of the
outfit. Does anyone have any experience of these? I have set the custom
setting to allow use of aperture ring on the camera and set the MF/AF switch
to MF. One curious thing is that with no extension tube fitted, when
changing the mode switch the display shows Aperture Priority in most/all
modes as it should but with an extension ring fitted the display shows the
information relating to the selected mode EG: Change mode switch to Tv,
display reads shutter priority. I suspected the contact faces of the
extension tubes might be dirty and cleaned them with IPA (isopropyl alcohol,
not beer) but still no go. Any help and advice would be greatly appreciated.
Best regards, Peter Smith.
Anonymous
February 9, 2005 2:13:11 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Wed, 9 Feb 2005 10:37:30 -0000, Pedro wrote:

> Hi all,
> Can onyone help me resolve this problem please? I have a set of PKA-AF fit
> extension tubes (Jessop branded) which seem to have the necessary electrical
> contacts passing through them to suit A-Series lenses and the *istDS. If I
> fit my old standard Pentax-A 50mm f1.7 PKA lens directly to my *istDS the
> lens works as expected with the aperture ring set to 'A'. If I then place
> any or all of these tubes between the camera and lens the Av indicator on
> the camera shows only -.- and obviously reduces the capability of the
> outfit. Does anyone have any experience of these? I have set the custom
> setting to allow use of aperture ring on the camera and set the MF/AF switch
> to MF. One curious thing is that with no extension tube fitted, when
> changing the mode switch the display shows Aperture Priority in most/all
> modes as it should but with an extension ring fitted the display shows the
> information relating to the selected mode EG: Change mode switch to Tv,
> display reads shutter priority. I suspected the contact faces of the
> extension tubes might be dirty and cleaned them with IPA (isopropyl alcohol,
> not beer) but still no go. Any help and advice would be greatly appreciated.
> Best regards, Peter Smith.

Peter, the behaviour is completely consistent with the camera thinking it
has a non-A lens mounted, so it sounds like the contact that handles this
data is not making it through the tube. When a non-A lens is used all modes
except manual default to Av, so that's normal too.

If you want to know which contact is used, look at the body flange - the one
that looks slightly depressed compared with the others is a simple on/off
signal that tells the camera that an the aperture ring is in the "A"
position. The other contacts on an A lens tell the body what the maximum
aperture is so it knows how far to stop down to get the required taking
aperture.

--
John Bean

The wine urges me on, the bewitching wine, which sets even a wise man to
singing and to laughing gently and rouses him up to dance and brings forth
words which were better unspoken (Homer)
February 9, 2005 2:24:26 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Thanks John.

I have had a look at all of the contacts and tried each tube separately, all
with the same result. Can you confirm that these tubes should actually work
with my equipment as described? All of the contacts seem to match those on
the camera body except one. The camera body has one more contact than the
tubes. I think it is the one most anti-clockwise looking at the front of the
camera body. I have tried insulating that contact with a piece of thin paper
thinking that it might have been shorting to the rear face of the tube but
that didn't help.

I haven't checked with a volt meter yet but do you know if there are any
measurable voltages present on these pins when the camera is powered on. I
could then at least note the voltages on the camera, fit a tube, and measure
again to determine which, if any, pins aren't contacting. It seems odd to me
that all tubes behave in a similar way.

Regards, Pete Smith.

"John Bean" <waterfoot@gmail.com> wrote in message
news:z4j586h20t5a.dlg@waterfoot.net...
> On Wed, 9 Feb 2005 10:37:30 -0000, Pedro wrote:
>
>> Hi all,
>> Can onyone help me resolve this problem please? I have a set of PKA-AF
>> fit
>> extension tubes (Jessop branded) which seem to have the necessary
>> electrical
>> contacts passing through them to suit A-Series lenses and the *istDS. If
>> I
>> fit my old standard Pentax-A 50mm f1.7 PKA lens directly to my *istDS the
>> lens works as expected with the aperture ring set to 'A'. If I then place
>> any or all of these tubes between the camera and lens the Av indicator on
>> the camera shows only -.- and obviously reduces the capability of the
>> outfit. Does anyone have any experience of these? I have set the custom
>> setting to allow use of aperture ring on the camera and set the MF/AF
>> switch
>> to MF. One curious thing is that with no extension tube fitted, when
>> changing the mode switch the display shows Aperture Priority in most/all
>> modes as it should but with an extension ring fitted the display shows
>> the
>> information relating to the selected mode EG: Change mode switch to Tv,
>> display reads shutter priority. I suspected the contact faces of the
>> extension tubes might be dirty and cleaned them with IPA (isopropyl
>> alcohol,
>> not beer) but still no go. Any help and advice would be greatly
>> appreciated.
>> Best regards, Peter Smith.
>
> Peter, the behaviour is completely consistent with the camera thinking it
> has a non-A lens mounted, so it sounds like the contact that handles this
> data is not making it through the tube. When a non-A lens is used all
> modes
> except manual default to Av, so that's normal too.
>
> If you want to know which contact is used, look at the body flange - the
> one
> that looks slightly depressed compared with the others is a simple on/off
> signal that tells the camera that an the aperture ring is in the "A"
> position. The other contacts on an A lens tell the body what the maximum
> aperture is so it knows how far to stop down to get the required taking
> aperture.
>
> --
> John Bean
>
> The wine urges me on, the bewitching wine, which sets even a wise man to
> singing and to laughing gently and rouses him up to dance and brings forth
> words which were better unspoken (Homer)
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Anonymous
February 9, 2005 3:03:53 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Wed, 9 Feb 2005 11:24:26 -0000, Pedro wrote:
> I have had a look at all of the contacts and tried each tube separately, all
> with the same result. Can you confirm that these tubes should actually work
> with my equipment as described? All of the contacts seem to match those on
> the camera body except one. The camera body has one more contact than the
> tubes. I think it is the one most anti-clockwise looking at the front of the
> camera body.

Yes, it should work. The extra unused contact is the "digital" one used by
modern bodies and lenses to pass additional information like focal length an
distance, it's not a requirement.

All the others are dumb "short to ground" contacts. The recessed one we
already covered, the others define max and min apertures in a sort of binary
pattern.

The reason the "A" contact is recessed is historic. Early "A" lenses
retracted the spring loaded contact when moved from the "A" position, so
breaking the connection mechanically. More modern lenses leave the contact
in place and disconnect it inside the lens, achieving the same effect. It
seems likely that the contact on the ring doesn't protrude quite as much as
it needs to connect to the slightly recessed body contact. If this is so,
the camera will ignore all the other contacts and assume a dumb lens is
mounted. It's equally possible that they may work on some bodies and not
others. I'm not a fan of Jessops "own brand" goods I'm afraid. The Kenko (or
is that coffee??) tubes work fine and are as well-made as the hideously
expensive Pentax ones, though they're still not exactly cheap.

--
John Bean

Why is it drug addicts and computer afficionados are both called users?
(Clifford Stoll)
February 9, 2005 3:14:38 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

You could be right, the contacts on these tubes are smaller overall in all
respects. Pins are thinner, nylon insulators are thinner. The camera body
contacts are at least 25-50% larger. I'll have a close look at the mechanics
later. I'm not a big fan of Jessop gear either, these were on eBay at a
reasonable price.

Regards, Peter Smith.

"John Bean" <waterfoot@gmail.com> wrote in message
news:m7oezkav3and$.dlg@waterfoot.net...
> On Wed, 9 Feb 2005 11:24:26 -0000, Pedro wrote:
>> I have had a look at all of the contacts and tried each tube separately,
>> all
>> with the same result. Can you confirm that these tubes should actually
>> work
>> with my equipment as described? All of the contacts seem to match those
>> on
>> the camera body except one. The camera body has one more contact than the
>> tubes. I think it is the one most anti-clockwise looking at the front of
>> the
>> camera body.
>
> Yes, it should work. The extra unused contact is the "digital" one used by
> modern bodies and lenses to pass additional information like focal length
> an
> distance, it's not a requirement.
>
> All the others are dumb "short to ground" contacts. The recessed one we
> already covered, the others define max and min apertures in a sort of
> binary
> pattern.
>
> The reason the "A" contact is recessed is historic. Early "A" lenses
> retracted the spring loaded contact when moved from the "A" position, so
> breaking the connection mechanically. More modern lenses leave the contact
> in place and disconnect it inside the lens, achieving the same effect. It
> seems likely that the contact on the ring doesn't protrude quite as much
> as
> it needs to connect to the slightly recessed body contact. If this is so,
> the camera will ignore all the other contacts and assume a dumb lens is
> mounted. It's equally possible that they may work on some bodies and not
> others. I'm not a fan of Jessops "own brand" goods I'm afraid. The Kenko
> (or
> is that coffee??) tubes work fine and are as well-made as the hideously
> expensive Pentax ones, though they're still not exactly cheap.
>
> --
> John Bean
>
> Why is it drug addicts and computer afficionados are both called users?
> (Clifford Stoll)
Anonymous
February 9, 2005 3:47:28 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Wed, 9 Feb 2005 12:14:38 -0000, Pedro wrote:

> You could be right, the contacts on these tubes are smaller overall in all
> respects. Pins are thinner, nylon insulators are thinner. The camera body
> contacts are at least 25-50% larger. I'll have a close look at the mechanics
> later. I'm not a big fan of Jessop gear either, these were on eBay at a
> reasonable price.

There's a big advantage to be had - especially with more than one ring - in
ignoring the "A" functionality altogether and use the aperture ring in
manual mode. When you press the AEL button to meter it will take a stopped
down reading of the light that actually gets through, independent of the
uncertainty of the additional mechanical and electric contacts introduced by
the ring(s). I usually do this even with good quality rings that work
properly - with your Jessop brand it's a no-brainer.

BTW: the Pentax-A 50/1.7 is *exceptionally* good as a macro lens when
reversed, in which case you have no choice other than to use it manually :-)

--
John Bean

Computers can figure out all kinds of problems, except the things in the
world that just don't add up (James Magary)
Anonymous
February 13, 2005 5:19:34 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

I have just spent a couple of hours trying to figure out what might be wrong
with these PKA tubes . . . and failed. I have another set of tubes described
as 'Auto' but that only refers to the auto-diaphragm mechanism, they are PK
mount tubes (lacking the pass-through electrical contacts). Both the PKA and
the PK set work in exactly the same way on my outfit (istDS + PKA 50mm
f1.7). I have read and re-read the istDS manual and have determined that the
only camera mode which will work properly is M; this is the only mode which
closes the aperture down to whatever the aperture ring on the lens is set
to. Eventually I got some respectable results. By stopping down to f16 the
DOF is acceptible, which it certainly wasn't at full aperture (f1.7). The
Vivitar 6000AF ring flash works great in ttl flash mode. All in all I think
that 'M' mode and manual aperture setting is going to satisfy my macro/macro
flash requirements. With all that said, I really would like to understand
why these PKA tubes don't allow a PKA lens to work properly. As far as I can
tell, all the contacts seem to be OK and they make contact with the camera
body and lens OK. What this means of course is that I can't possibly use a
DA series lens, like the kit lens, because it has no aperture ring.

Peter Smith.

"John Bean" <waterfoot@gmail.com> wrote in message
news:98l7wqqbvq1x.dlg@waterfoot.net...
> On Wed, 9 Feb 2005 12:14:38 -0000, Pedro wrote:
>
>> You could be right, the contacts on these tubes are smaller overall in
>> all
>> respects. Pins are thinner, nylon insulators are thinner. The camera body
>> contacts are at least 25-50% larger. I'll have a close look at the
>> mechanics
>> later. I'm not a big fan of Jessop gear either, these were on eBay at a
>> reasonable price.
>
> There's a big advantage to be had - especially with more than one ring -
> in
> ignoring the "A" functionality altogether and use the aperture ring in
> manual mode. When you press the AEL button to meter it will take a stopped
> down reading of the light that actually gets through, independent of the
> uncertainty of the additional mechanical and electric contacts introduced
> by
> the ring(s). I usually do this even with good quality rings that work
> properly - with your Jessop brand it's a no-brainer.
>
> BTW: the Pentax-A 50/1.7 is *exceptionally* good as a macro lens when
> reversed, in which case you have no choice other than to use it manually
> :-)
>
> --
> John Bean
>
> Computers can figure out all kinds of problems, except the things in the
> world that just don't add up (James Magary)
Anonymous
February 13, 2005 12:27:05 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Sun, 13 Feb 2005 02:19:34 -0000, Pete Smith wrote:

> I have just spent a couple of hours trying to figure out what might be wrong
> with these PKA tubes . . . and failed. I have another set of tubes described
> as 'Auto' but that only refers to the auto-diaphragm mechanism, they are PK
> mount tubes (lacking the pass-through electrical contacts). Both the PKA and
> the PK set work in exactly the same way on my outfit (istDS + PKA 50mm
> f1.7). I have read and re-read the istDS manual and have determined that the
> only camera mode which will work properly is M; this is the only mode which
> closes the aperture down to whatever the aperture ring on the lens is set
> to. Eventually I got some respectable results. By stopping down to f16 the
> DOF is acceptible, which it certainly wasn't at full aperture (f1.7). The
> Vivitar 6000AF ring flash works great in ttl flash mode. All in all I think
> that 'M' mode and manual aperture setting is going to satisfy my macro/macro
> flash requirements. With all that said, I really would like to understand
> why these PKA tubes don't allow a PKA lens to work properly. As far as I can
> tell, all the contacts seem to be OK and they make contact with the camera
> body and lens OK. What this means of course is that I can't possibly use a
> DA series lens, like the kit lens, because it has no aperture ring.

Yes, you need the contacts to use a lens with no aperture ring of course,
but other than that there's no advantage to be had. If you want to use the
tubes other than with flash don't forget that pressing AEL in manual mode
will do automatic stop-down metering and set the shutter speed accordingly -
almost as convenient as aperture priority and *much* more accurate when
using tubes.


--
John Bean

If the automobile had followed the same development cycle as the computer, a
Rolls-Royce would today cost $100, get a million miles per gallon, and
explode once a year, killing everyone inside (Robert X. Cringely)
Anonymous
February 13, 2005 2:39:18 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Thanks John.

All manual it is then and I'm happy with that. Now I know the limitations I
can work with it. I think I'll stick to my Vivitar PK set of tubes, they are
better quality, tighter fit, better finish, etc. I might invest in a set of
Kenko tubes at some point but you're right they are expensive and I'd
certainly prefer to 'try before buy' based on my current experience.

If anyone following this thread wants a set of Jessop branded PKA Auto
extension tubes . . . keep an eye on eBay where all my redundant Pentax gear
will be appearing shortly under username 'Mannesty'. You will have gathered
by now that they don't work with a Pentax istDS but I've no reason to
suspect that they will be any trouble on an older 'analogue' PK-A compatible
camera.

Thanks again for your valued assistance John, regards, Pete Smith.

"John Bean" <waterfoot@gmail.com> wrote in message
news:15ok9pk357ig3.dlg@waterfoot.net...
> On Sun, 13 Feb 2005 02:19:34 -0000, Pete Smith wrote:
>
>> I have just spent a couple of hours trying to figure out what might be
>> wrong
>> with these PKA tubes . . . and failed. I have another set of tubes
>> described
>> as 'Auto' but that only refers to the auto-diaphragm mechanism, they are
>> PK
>> mount tubes (lacking the pass-through electrical contacts). Both the PKA
>> and
>> the PK set work in exactly the same way on my outfit (istDS + PKA 50mm
>> f1.7). I have read and re-read the istDS manual and have determined that
>> the
>> only camera mode which will work properly is M; this is the only mode
>> which
>> closes the aperture down to whatever the aperture ring on the lens is set
>> to. Eventually I got some respectable results. By stopping down to f16
>> the
>> DOF is acceptible, which it certainly wasn't at full aperture (f1.7). The
>> Vivitar 6000AF ring flash works great in ttl flash mode. All in all I
>> think
>> that 'M' mode and manual aperture setting is going to satisfy my
>> macro/macro
>> flash requirements. With all that said, I really would like to understand
>> why these PKA tubes don't allow a PKA lens to work properly. As far as I
>> can
>> tell, all the contacts seem to be OK and they make contact with the
>> camera
>> body and lens OK. What this means of course is that I can't possibly use
>> a
>> DA series lens, like the kit lens, because it has no aperture ring.
>
> Yes, you need the contacts to use a lens with no aperture ring of course,
> but other than that there's no advantage to be had. If you want to use the
> tubes other than with flash don't forget that pressing AEL in manual mode
> will do automatic stop-down metering and set the shutter speed
> accordingly -
> almost as convenient as aperture priority and *much* more accurate when
> using tubes.
>
>
> --
> John Bean
>
> If the automobile had followed the same development cycle as the computer,
> a
> Rolls-Royce would today cost $100, get a million miles per gallon, and
> explode once a year, killing everyone inside (Robert X. Cringely)
Anonymous
February 13, 2005 10:38:41 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

In article <420f3c5b$0$441$ed2619ec@ptn-nntp-reader02.plus.net>,
Pete Smith <peter.smith@manNOSPAMnesty.com> wrote:
>
>If anyone following this thread wants a set of Jessop branded PKA Auto
>extension tubes . . . keep an eye on eBay where all my redundant Pentax gear
>will be appearing shortly under username 'Mannesty'. You will have gathered
>by now that they don't work with a Pentax istDS but I've no reason to
>suspect that they will be any trouble on an older 'analogue' PK-A compatible
>camera.

That is most certainly untrue. The problem is most likely to lie in the "A"
pin itself failing to make contact on your body, your lens, or one of the
intermediate contacts between the different tubes.

That problem will show up on older PK-A compatible cameras just as much as on
a *ist-D. I've run into exactly that problem with some lens/TC combinations
on my PZ-1p; combinations that work without any problems on my *ist-D.

It's *possible* the tubes would work fine on an older body. It's also quite
possible that they will still fail to work - maybe only intermittently, maybe
quite consistently.
Anonymous
February 13, 2005 11:35:15 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Thanks for the info John. I'm reasonably sure it is a tube - camera body
issue as I have a number of A series lenses all showing the same problem.
Further, I get the problem with all 3 tubes even when fitted separately. If
I fit the tube(s) to either the body or the lens the pins 'feel' OK in that
the spring pressure can be felt. The pins in the tubes are not spring biased
in any way, just free floating. When fitted to either a lens or the istDS
however, the spring tension is definitely there. That of course doesn't mean
that they are making a good electrical contact. I wondered if some of the
other pins were shorting to the tubes mount but that is very difficult to
check. It would be easier to check if I knew what voltages or waveforms
would normally be present on those pins. I have both an oscilloscope and a
DMM to measure such things. I think I might just fire up the 'scope and have
a look anyway, out of curiosity.
"John Francis" <johnf@panix.com> wrote in message
news:cuoac1$gn2$1@reader2.panix.com...
> In article <420f3c5b$0$441$ed2619ec@ptn-nntp-reader02.plus.net>,
> Pete Smith <peter.smith@manNOSPAMnesty.com> wrote:
>>
>>If anyone following this thread wants a set of Jessop branded PKA Auto
>>extension tubes . . . keep an eye on eBay where all my redundant Pentax
>>gear
>>will be appearing shortly under username 'Mannesty'. You will have
>>gathered
>>by now that they don't work with a Pentax istDS but I've no reason to
>>suspect that they will be any trouble on an older 'analogue' PK-A
>>compatible
>>camera.
>
> That is most certainly untrue. The problem is most likely to lie in the
> "A"
> pin itself failing to make contact on your body, your lens, or one of the
> intermediate contacts between the different tubes.
>
> That problem will show up on older PK-A compatible cameras just as much as
> on
> a *ist-D. I've run into exactly that problem with some lens/TC
> combinations
> on my PZ-1p; combinations that work without any problems on my *ist-D.
>
> It's *possible* the tubes would work fine on an older body. It's also
> quite
> possible that they will still fail to work - maybe only intermittently,
> maybe
> quite consistently.
>
>
>
Anonymous
February 14, 2005 12:31:13 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

I don't know whether you'll be able to test anything useful.
My primary suspicion would focus on the actual "A"-pin-to-body
contact. I suppose you could try just mounting the tubes,
with no lens attached, and see if things changed as you
pushed on the lens end of the "A" pin.

On an "A" lens mount there would be no voltages or waveforms
on the pins. The only difference is whether or not the pin
is short-circuited to the lens mount, or open circuit.

The presence of an "A" lens (at the "A" setting) is detected
by the fact that the "A" pin is shorted to the mount. On an
actual "A" lens this is done by mechanically moving the pin;
on the later mount variations it is switched internally.

You should be able to measure this easily enough on a lens,
but how you measure whether the "A" pin is making contact
with the body is rather harder.


In article <420fb9df$0$7935$ed2619ec@ptn-nntp-reader01.plus.net>,
Pete Smith <peter.smith@manNOSPAMnesty.com> wrote:
>Thanks for the info John. I'm reasonably sure it is a tube - camera body
>issue as I have a number of A series lenses all showing the same problem.
>Further, I get the problem with all 3 tubes even when fitted separately. If
>I fit the tube(s) to either the body or the lens the pins 'feel' OK in that
>the spring pressure can be felt. The pins in the tubes are not spring biased
>in any way, just free floating. When fitted to either a lens or the istDS
>however, the spring tension is definitely there. That of course doesn't mean
>that they are making a good electrical contact. I wondered if some of the
>other pins were shorting to the tubes mount but that is very difficult to
>check. It would be easier to check if I knew what voltages or waveforms
>would normally be present on those pins. I have both an oscilloscope and a
>DMM to measure such things. I think I might just fire up the 'scope and have
>a look anyway, out of curiosity.
>"John Francis" <johnf@panix.com> wrote in message
>news:cuoac1$gn2$1@reader2.panix.com...
>> In article <420f3c5b$0$441$ed2619ec@ptn-nntp-reader02.plus.net>,
>> Pete Smith <peter.smith@manNOSPAMnesty.com> wrote:
>>>
>>>If anyone following this thread wants a set of Jessop branded PKA Auto
>>>extension tubes . . . keep an eye on eBay where all my redundant Pentax
>>>gear
>>>will be appearing shortly under username 'Mannesty'. You will have
>>>gathered
>>>by now that they don't work with a Pentax istDS but I've no reason to
>>>suspect that they will be any trouble on an older 'analogue' PK-A
>>>compatible
>>>camera.
>>
>> That is most certainly untrue. The problem is most likely to lie in the
>> "A"
>> pin itself failing to make contact on your body, your lens, or one of the
>> intermediate contacts between the different tubes.
>>
>> That problem will show up on older PK-A compatible cameras just as much as
>> on
>> a *ist-D. I've run into exactly that problem with some lens/TC
>> combinations
>> on my PZ-1p; combinations that work without any problems on my *ist-D.
>>
>> It's *possible* the tubes would work fine on an older body. It's also
>> quite
>> possible that they will still fail to work - maybe only intermittently,
>> maybe
>> quite consistently.
>>
>>
>>
>
>
Anonymous
February 14, 2005 12:59:08 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Easy, with lens & tube removed short the 'A' pin to the camera body, fit the
tube to the body and repeat. That should 'fool' the body. I'll try it and
report back.

"John Francis" <johnf@panix.com> wrote in message
news:cuogv1$mkq$1@reader2.panix.com...
>I don't know whether you'll be able to test anything useful.
> My primary suspicion would focus on the actual "A"-pin-to-body
> contact. I suppose you could try just mounting the tubes,
> with no lens attached, and see if things changed as you
> pushed on the lens end of the "A" pin.
>
> On an "A" lens mount there would be no voltages or waveforms
> on the pins. The only difference is whether or not the pin
> is short-circuited to the lens mount, or open circuit.
>
> The presence of an "A" lens (at the "A" setting) is detected
> by the fact that the "A" pin is shorted to the mount. On an
> actual "A" lens this is done by mechanically moving the pin;
> on the later mount variations it is switched internally.
>
> You should be able to measure this easily enough on a lens,
> but how you measure whether the "A" pin is making contact
> with the body is rather harder.
>
>
> In article <420fb9df$0$7935$ed2619ec@ptn-nntp-reader01.plus.net>,
> Pete Smith <peter.smith@manNOSPAMnesty.com> wrote:
>>Thanks for the info John. I'm reasonably sure it is a tube - camera body
>>issue as I have a number of A series lenses all showing the same problem.
>>Further, I get the problem with all 3 tubes even when fitted separately.
>>If
>>I fit the tube(s) to either the body or the lens the pins 'feel' OK in
>>that
>>the spring pressure can be felt. The pins in the tubes are not spring
>>biased
>>in any way, just free floating. When fitted to either a lens or the istDS
>>however, the spring tension is definitely there. That of course doesn't
>>mean
>>that they are making a good electrical contact. I wondered if some of the
>>other pins were shorting to the tubes mount but that is very difficult to
>>check. It would be easier to check if I knew what voltages or waveforms
>>would normally be present on those pins. I have both an oscilloscope and a
>>DMM to measure such things. I think I might just fire up the 'scope and
>>have
>>a look anyway, out of curiosity.
>>"John Francis" <johnf@panix.com> wrote in message
>>news:cuoac1$gn2$1@reader2.panix.com...
>>> In article <420f3c5b$0$441$ed2619ec@ptn-nntp-reader02.plus.net>,
>>> Pete Smith <peter.smith@manNOSPAMnesty.com> wrote:
>>>>
>>>>If anyone following this thread wants a set of Jessop branded PKA Auto
>>>>extension tubes . . . keep an eye on eBay where all my redundant Pentax
>>>>gear
>>>>will be appearing shortly under username 'Mannesty'. You will have
>>>>gathered
>>>>by now that they don't work with a Pentax istDS but I've no reason to
>>>>suspect that they will be any trouble on an older 'analogue' PK-A
>>>>compatible
>>>>camera.
>>>
>>> That is most certainly untrue. The problem is most likely to lie in
>>> the
>>> "A"
>>> pin itself failing to make contact on your body, your lens, or one of
>>> the
>>> intermediate contacts between the different tubes.
>>>
>>> That problem will show up on older PK-A compatible cameras just as much
>>> as
>>> on
>>> a *ist-D. I've run into exactly that problem with some lens/TC
>>> combinations
>>> on my PZ-1p; combinations that work without any problems on my *ist-D.
>>>
>>> It's *possible* the tubes would work fine on an older body. It's also
>>> quite
>>> possible that they will still fail to work - maybe only intermittently,
>>> maybe
>>> quite consistently.
>>>
>>>
>>>
>>
>>
>
>
Anonymous
February 14, 2005 1:26:06 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Sun, 13 Feb 2005 20:35:15 -0000, Pete Smith wrote:

> Thanks for the info John. I'm reasonably sure it is a tube - camera body
> issue as I have a number of A series lenses all showing the same problem.

That's a new one, you didn't say that before. Points to a problem with the
body in that case.

> It would be easier to check if I knew what voltages or waveforms
> would normally be present on those pins. I have both an oscilloscope and a
> DMM to measure such things. I think I might just fire up the 'scope and have
> a look anyway, out of curiosity.

All the contacts that go through the tube are just switch to ground signals,
not helpful. They determine min and max apertures as I said earlier and are
ignored anyhow if the "A" pin is not grounded.


--
John Bean

When I read about the evils of drinking, I gave up reading (Henny Youngman)
Anonymous
February 14, 2005 1:49:37 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

This is what I have discovered so far.

'A' Series lens fitted to camera in Auto Picture mode shows both shutter and
aperture info. Expected behaviour.

With no lens fitted, only shutter info appears, aperture info shows -.- and
when shutter pressed halfway, nothing much else happens, shutter will not
release if shutter button fully pressed. Expected behaviour.

With no lens fitted, short the 'A' pin to camera lens flange, press shutter
button halfway and flash pops up. Shutter releases if button fully pressed.
This means that shorting the 'A' pin to the camera body 'fools' the camera,
but not completely because aperture info is still showing -.- This is
certainly a different behaviour but I don't know if it is normal.

Fit a tube and a lens, same behaviour as with no lens fitted and shorting
'A' pin to body, therefore 'A' pin must be connecting through the tube to
the camera body. Still the aperture info shows -.-

There are 2 other pins on my 'A' series lens. one looks like a polythene
insulator (2nd pin anticlockwise from the 'A' Pin looking at the camera
body), the other a solid (grounded) contact (2nd pin clockwise from the 'A'
pin looking at the camera body).

I need about 3 pairs of hands to try and simulate all three, but I'll try.

In the meantime, if the above info triggers any thoughts, I'll be happy to
hear them.

"John Bean" <waterfoot@gmail.com> wrote in message
news:6xes9ij8alpz.dlg@waterfoot.net...
> On Sun, 13 Feb 2005 20:35:15 -0000, Pete Smith wrote:
>
>> Thanks for the info John. I'm reasonably sure it is a tube - camera body
>> issue as I have a number of A series lenses all showing the same problem.
>
> That's a new one, you didn't say that before. Points to a problem with the
> body in that case.
>
>> It would be easier to check if I knew what voltages or waveforms
>> would normally be present on those pins. I have both an oscilloscope and
>> a
>> DMM to measure such things. I think I might just fire up the 'scope and
>> have
>> a look anyway, out of curiosity.
>
> All the contacts that go through the tube are just switch to ground
> signals,
> not helpful. They determine min and max apertures as I said earlier and
> are
> ignored anyhow if the "A" pin is not grounded.
>
>
> --
> John Bean
>
> When I read about the evils of drinking, I gave up reading (Henny
> Youngman)
Anonymous
February 14, 2005 2:44:17 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

In article <420fd95d$0$51875$ed2619ec@ptn-nntp-reader01.plus.net>,
Pete Smith <peter.smith@manNOSPAMnesty.com> wrote:
>This is what I have discovered so far.
>
>Fit a tube and a lens, same behaviour as with no lens fitted and shorting
>'A' pin to body, therefore 'A' pin must be connecting through the tube to
>the camera body.

But maybe you're moving the "A" pin onto the contact when you create
the short? Are you sure you're not pushing the pin any further than
mounting an actual "A" lens mould push it?

>
>There are 2 other pins on my 'A' series lens. one looks like a polythene
>insulator (2nd pin anticlockwise from the 'A' Pin looking at the camera
>body), the other a solid (grounded) contact (2nd pin clockwise from the 'A'
>pin looking at the camera body).

These indicate maximum & minimum aperture (f1.7 & f22 in this case).
See <http://www.bdimitrov.de/kmp/&gt; for further technical details.
Anonymous
February 14, 2005 3:33:28 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Eureka, I have found the answer. This problem is caused by the extra pin on
the camera body. It needs to short to ground. This it does when a lens is
fitted, but fit an anadised (maybe painted) aluminium extension tube . . .
it doesn't short to ground any more. The remedy . . . grind off the
anadising on each ring in the place where the extra body pin is. I was a
little worried that I would not be able to use more than one ring at a time
because of the lack of pass-through connectivity. Having tried all
combinations it works like a dream.

Sorry guys, these tubes will not be appearing on any auction site (we can't
mention eBay) in the near future.

John & John, thanks for your feedback. It would have taken me a lot longer
to 'fix' this without your collective help.

Regards, Peter Smith.

"Pete Smith" <peter.smith@manNOSPAMnesty.com> wrote in message
news:420fd95d$0$51875$ed2619ec@ptn-nntp-reader01.plus.net...
> This is what I have discovered so far.
>
> 'A' Series lens fitted to camera in Auto Picture mode shows both shutter
> and aperture info. Expected behaviour.
>
> With no lens fitted, only shutter info appears, aperture info shows -.-
> and when shutter pressed halfway, nothing much else happens, shutter will
> not release if shutter button fully pressed. Expected behaviour.
>
> With no lens fitted, short the 'A' pin to camera lens flange, press
> shutter button halfway and flash pops up. Shutter releases if button fully
> pressed. This means that shorting the 'A' pin to the camera body 'fools'
> the camera, but not completely because aperture info is still showing -.-
> This is certainly a different behaviour but I don't know if it is normal.
>
> Fit a tube and a lens, same behaviour as with no lens fitted and shorting
> 'A' pin to body, therefore 'A' pin must be connecting through the tube to
> the camera body. Still the aperture info shows -.-
>
> There are 2 other pins on my 'A' series lens. one looks like a polythene
> insulator (2nd pin anticlockwise from the 'A' Pin looking at the camera
> body), the other a solid (grounded) contact (2nd pin clockwise from the
> 'A' pin looking at the camera body).
>
> I need about 3 pairs of hands to try and simulate all three, but I'll try.
>
> In the meantime, if the above info triggers any thoughts, I'll be happy to
> hear them.
>
> "John Bean" <waterfoot@gmail.com> wrote in message
> news:6xes9ij8alpz.dlg@waterfoot.net...
>> On Sun, 13 Feb 2005 20:35:15 -0000, Pete Smith wrote:
>>
>>> Thanks for the info John. I'm reasonably sure it is a tube - camera body
>>> issue as I have a number of A series lenses all showing the same
>>> problem.
>>
>> That's a new one, you didn't say that before. Points to a problem with
>> the
>> body in that case.
>>
>>> It would be easier to check if I knew what voltages or waveforms
>>> would normally be present on those pins. I have both an oscilloscope and
>>> a
>>> DMM to measure such things. I think I might just fire up the 'scope and
>>> have
>>> a look anyway, out of curiosity.
>>
>> All the contacts that go through the tube are just switch to ground
>> signals,
>> not helpful. They determine min and max apertures as I said earlier and
>> are
>> ignored anyhow if the "A" pin is not grounded.
>>
>>
>> --
>> John Bean
>>
>> When I read about the evils of drinking, I gave up reading (Henny
>> Youngman)
>
>
Anonymous
February 14, 2005 11:06:22 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Mon, 14 Feb 2005 00:33:28 -0000, Pete Smith wrote:

> Eureka, I have found the answer. This problem is caused by the extra pin on
> the camera body. It needs to short to ground. This it does when a lens is
> fitted, but fit an anadised (maybe painted) aluminium extension tube . . .
> it doesn't short to ground any more. The remedy . . . grind off the
> anadising on each ring in the place where the extra body pin is. I was a
> little worried that I would not be able to use more than one ring at a time
> because of the lack of pass-through connectivity. Having tried all
> combinations it works like a dream.
>
> Sorry guys, these tubes will not be appearing on any auction site (we can't
> mention eBay) in the near future.
>
> John & John, thanks for your feedback. It would have taken me a lot longer
> to 'fix' this without your collective help.

Very odd, but I've learned something new. The "extra" pin is the digital
interface used by chipped lenses, but of course the metal mount of an old
lens will short this to ground. The camera shouldn't care one way or the
other but clearly it does. I'll remember that, useful information.

--
John Bean

Part of the inhumanity of the computer is that, once it is competently
programmed and working smoothly, it is completely honest (Isaac Asimov)
!