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11-23-2014, 11:46 AM   #1
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Teleconverter contacts

Hello all


As usual with my few previous posts, I apologise if this is covered elsewhere; I have looked quite extensively in these forums but not found any definitive answer.


My essential question is this: I am looking for a 2x MC7 TC (Pentax K mount) which will allow me to alter aperture. Most images in ebay show TCs with a plain flange, no pins present, even though at least a couple of those currently posted on ebay claim that "metering" is possible. A very few show six or seven round pins, which I believe are the data and power connections between camera and lens. Do the plain-flanged, pin-less TCs provide any control over aperture? I am sure they don't but in case I am missing something, I'd like to know for sure so that I don't have to do so much dithering around on ebay.


You can all turn off now but as a bit of background - and in case anyone is able to stop me making a huge mistake or offer other advice, please feel free to read on:


I bought a Teleplus 2x MC4 KAX TC (with six pins) and its works fine - I can control the aperture. Oddly, the camera reports a wide-open aperture of f/1.2 on my Sigma 70mm f/2.8 macro lens; no matter, my macro photography will be mostly trial-and-error and I can be patient, sometimes.


By the way, my intention is to remove the glass and use this Teleplus as an extension tube with contacts - something I haven't yet dared to do.


The reason I want a 2x MC7 is that it has a flange-to-flange distance of about fifty percent longer than the MC4 (guessed from ebay images) and the set of two will allow me a decent mix of variable extension (an idea I think I once read somewhere on these forums).


Another "by the way": In my search for a macro set up that suits me - both indoors and out in our beautiful countryside - I also bought a set of simple extension tubes (no pins) and (yet to be delivered) an Asahi bellows unit. These, I am fairly certain, offer no control over aperture but after watching some stuff on YouTube, I found that wedging the lens's aperture control thingy works fairly well, so that on attaching the lens to the camera, the aperture opens only as far as the wedge allows. Faced with the prospect of making a set of different wedges to give me some rough control over aperture, I have instead decided to go with the glass-less TC option, though of course for the bellows I will still need to take the wedge route - unless someone has a different magic trick?


K5 II - my final "by the way".


Best wishes and regards


Steve

11-23-2014, 01:06 PM   #2
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If the tubes have an aperture lever and a conductive lens mount the lens will close the aperture down on K-mount lens in Manual mode. If the tubes have contacts and it is an "A" type lens the aperture can be set via the eDial when the lens is in "A" mode.

Some Sigma lenses seem to give problems using tubes or TCs. It could be that they are using the 7th "data" pin and you need a 7 pin tube for them to handshake with the camera. Sometimes they work properly on a 6 pin tube but not a 7 pin.

If you are using the Pentax Auto Bellows K, M or A you have to stop the lenses down manually. "A" lenses are used off the "A" mode. There is a locking DOF preview button or you can use a locking mechanical cable release. With the camera set for using manual focus lenses (use aperture ring enabled, Green button in M and TAv set to Tv shift and DOF preview set to optical) operation is similar to using M42 lenses. In Manual mode: Focus and compose wide open. Set the aperture and stop down the lens with DOF preview button on the bellows or with the cable. On the K5-II you then press the green button which will set the shutter speed. Or you can use the camera DOF which will activate the exposure bars and you "zero" the exposure by changing the aperture ring and the shutters speed with the eDial.

If the lens does not have an aperture ring you could try pressing the lens release lever and rotating the lens until it stops down. You can control the size of the iris pupil by the position you rotate the lens to. Of course you risk the lens falling off the mount. Note the lens release lever works differently on the bellows - you press it in towards the bellows standard and not back towards the camera body.
11-23-2014, 01:11 PM   #3
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Maybe this will help. Attached are pictures of my 2X Kenco. As you can see it has 7 contacts plus 2 brass contacts front and rear. It works perfectly in auto.
QuoteOriginally posted by Deep Dene Steve Quote
Do the plain-flanged, pin-less TCs provide any control over aperture? I am sure they don't but in case I am missing something
I would have to believe you would have to work in M mode, select your aperture and use the green button.

---------- Post added 11-23-14 at 03:13 PM ----------

I can post a test shot with the Kenco if you like.
11-23-2014, 01:15 PM   #4
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I don't know where the pix went. Let's try again. Notice there are brass contacts also.

Attached Images
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PENTAX K-5  Photo 
View Picture EXIF
PENTAX K-5  Photo 
11-23-2014, 01:18 PM   #5
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Sample shots with Kenco. They are not from the same position, I tried to make images the same size and did not succeed.
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PENTAX K-5  Photo 
View Picture EXIF
PENTAX K-5  Photo 
11-27-2014, 01:13 PM   #6
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Thanks guys for your responses. I have decided to resolve my problem by taking what to me is a simple path. I've bought a second MC4 teleconverter (with pins), having successfully removed the glass from the first one I bought. The two together will give me an extension of 48mm and I am content with that prospect for outdoor macro work and aperture control. The "nice to have" versatility that an MC7 would have offered is perhaps no longer a big deal for me - I'm sure I have all that I need with two MC4s; the MC7s with pins were proving difficult to obtain (outbid at every move).


My plain-flange, pinless tubes are now part of my bellows set-up. with which I intend to use an old A lens that I can control via the bellows' remote thingie.


As to the essential point of my OP, "Not a Number"''s reply: "If the tubes have an aperture lever and a conductive lens mount the lens will close the aperture down on K-mount lens in Manual mode."


Well, the tubes have what looks like an aluminium face (presumably conductive) and an internal aperture lever but no pins at all. No permutation of settings between a modern, aperture-ringless-lens and my K5 II allows me to control aperture. I might possibly be missing something but as above, my problem drifts off into the ether, as soon as my new (old) A lens lands on the doorstep.


Thanks and regards


Steve
11-27-2014, 04:24 PM   #7
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QuoteOriginally posted by Deep Dene Steve Quote
Well, the tubes have what looks like an aluminium face (presumably conductive) and an internal aperture lever but no pins at all. No permutation of settings between a modern, aperture-ringless-lens and my K5 II allows me to control aperture. I might possibly be missing something but as above, my problem drifts off into the ether, as soon as my new (old) A lens lands on the doorstep.
With a non-conductive mount the aperture stop-down lever will not actuate on some bodies. With a conductive mount the lever will actuate on DOF preview, green button and during the exposure in manual mode. By actuating I mean it will stop down the lens. That is what I said before " "If the tubes have an aperture lever and a conductive lens mount the lens will close the aperture down on K-mount lens in Manual mode."

You need to short out the "A" pin in order to control the aperture on lenses without aperture ring. A conductive lens mount without an "A" pin will not do this as the "A" contact on female (camera) side is recessed. You can short out the "A" pin by putting a ball of metal foil or removing the mount a putting a strip of foil over the "A" pin but without the minimum/maximum settings through the contacts or the 7th data pin the body will use the incorrect minimum/maximum apertures and your f-stop settings will be off.

With mounts without contacts you can only set the aperture with an aperture ring. With "A" series lenses take it out of "A" mode and treat it as a "M" or "K" series lens.

I never said a plain conductive mount will allow you to control the aperture setting (f-stop).
12-13-2014, 11:13 AM   #8
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Please excuse the late response but I've been stuck inside a bellows for a couple of weeks. For my outdoors stuff, the two glassless 2x teleconverters are giving me plenty to get to grips with for now. Sorry Not a Number, to have misinterpreted your post, put it down to noob naivety. Once I have become properly familiar with what I have, I will revisit all of the above advice and make sure I understand it all. Thanks again, to all.

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