Pentax PKA-AF Extension Tube problem

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.

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)

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" wrote in message
...
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)

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)

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" wrote in message
...
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)

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)

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" wrote in message
...
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)

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)

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" wrote in message
...
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)

In article ,
Pete Smith 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.