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12-29-2012, 07:31 AM   #1
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Pentax FA 100mm 2.8 macro + Sigma 1.4x EX DG TC problem

When I use this combination,I cant AF and the top display doesnt show the aperture number. I know this lens is not in the compatibility list, but I have read in this forum that some can use this combination. Is this normal or did I get a defective TC?

12-29-2012, 08:05 AM   #2
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Make sure the aperture ring on the FA 100 Macro is at "A"
12-29-2012, 08:15 AM   #3
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QuoteOriginally posted by LeDave Quote
Make sure the aperture ring on the FA 100 Macro is at "A"
yes. it is set at A.
12-29-2012, 02:57 PM   #4
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Not sure what's wrong, maybe the lens is not compatible with the teleconverter like you said, have you tried a different lens on it?

12-29-2012, 05:00 PM   #5
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I have tried with my pentax a 50 1.7 and it still gives me the same result.
12-29-2012, 06:39 PM   #6
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QuoteOriginally posted by azerak Quote
When I use this combination,I cant AF and the top display doesnt show the aperture number. I know this lens is not in the compatibility list, but I have read in this forum that some can use this combination. Is this normal or did I get a defective TC?
Hi azerak,

First of all, Sigma doesn't list any non-Sigma lenses on their compatibility chart, so this really means nothing. The only thing that might prevent compatibility with either of the Sigma TCs is the protruding front elements that they use which can prevent a given lens from mounting on the TC if the lens doesn't have a rear element that's sufficiently recessed, or the cavity in the rear of the lens is not large enough to accommodate the diameter of the front element of the TC with it's surrounding support. My D FA 100 f2.8 Macro does mount and functions correctly with my Sigma EX 1.4x APO AF TC, but both are different models than you have, and there might be slight differences in either or both.

QuoteOriginally posted by azerak Quote
I have tried with my pentax a 50 1.7 and it still gives me the same result.
I don't have an A 50 f1.7, but I do have an A 50 f2.8 Macro, an F 50 f1.7, a S-M-C Tak 50 f1.4 with an OEM M42 to K adapter, and an FA 50 f1.4, and none of them have recessed rear elements, so none of them even remotely comes close to mounting on the Sigma EX 1.4x APO TC. I do know that the APO DG is not sufficiently different to allow any of these lenses to mount.

At this point, I don't know what to suggest here.

Scott
12-29-2012, 09:51 PM   #7
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I have read somewhere in this forum before that some people got them to work. That was the reason that I got the TC. From the looks of it, the protruding element of the TC doesnt interfere the element of the lens. Just in case, here I attach the pictures of both of them.

The TC





The lens



Though a review said only Sigma lenses, 'Im still optimist.

Sigma 1.4x DG EX APO Teleconverter Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database
12-29-2012, 11:07 PM   #8
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Ok now I am out, I'm at a lost on how to help you out. However I hope someone comes by and finds your solution!

12-30-2012, 01:41 AM   #9
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Hi azerak,

Perhaps I wasn't clear. The point of the first paragraph in my previous post was that the compatibility issue is essentially that it is solely a matter of whether the lens will actually physically mount on the TC or not because of the protruding front element. If it does, it should both AF with an AF capable lens and show the aperture value (though this will just be passed through, and will not show the actual f-stop value with the TC accounted for). The lens must fully mount, with the lens lock on the TC actually clicking into the corresponding groove in the lens' mount and the TC mounting to the camera in the same manner -- if these do not happen, the pins of the lens and those of the TC will not align correctly nor make contact, and the AF and aperture control functions will not work.

If your lens and TC do indeed mount completely, then there might be some reason that the pins aren't passing the required information to the camera. This can be corrosion or contamination on the data or "A" pin. (Edit) -- here's a link to a page that illustrates the locations of the pins (OK -- this works -- Thanks lytrytyr - it worked in the preview. . .):

http://www.robertstech.com/matrix.htm

The information that the Data pin carries to the camera is that the lens is an AF lens. The information that the A pin carries is the aperture information. The other pins are essentially irrelevant to your problem as they only indicate min and max aperture information when either open or insulated in combination.

The problems can arise from non-contact from the lens, the camera mount, or either side of the TC. Since the lens seems to work when used by itself, the most likely cause is one or both sides of the TC. I'd first try to rotate the lens on the TC, then the TC on the camera mount. Slight amounts of play in the lens lock mechanisms could cause a misalignment of the contacts. You can watch the Av display on the top of the camera to see if this has any effect. If the Av appears momentarily, then goes back to f---, then try AF when the Av is showing. If Av does not appear, I'd try cleaning the contacts.

I'd clean only the contacts involved, starting with both sides of the TC, try it with the lens and camera, and go to the contacts on both the lens and camera mounts if you get no improvement. Don't assume anything. Use a pencil erasure, and rub the tip of the pins, then blow any debris clear of the lens carefully with a bulb blower. Others have had success using a dedicated electrical contact cleaning fluid on a Q tip or with a similar delivery device, then letting it dry completely before mounting. Do not spray the lens mount directly. Remove any residue left by the contact cleaner with a clean micro fiber or lintless cotton cloth.

If neither of these work, then I'd assume that something is amiss with the TC for your gear. This is not to say it's defective, it just doesn't work with your gear. This happens, and it's nobody's fault in particular. I'd respectfully ask for a replacement or refund without placing fault. At this point, you've made every reasonable effort to make it work, and any reasonable seller should accept the return, if that possibility was allowed for in the purchase agreement.

The second paragraph of my previous post was expressing doubt that you could actually mount any Pentax 50mm lens on the Sigma TC as you had stated in the quoted post. This is an example of why Sigma TCs are not compatible with a number of lenses.

Scott

Last edited by snostorm; 12-30-2012 at 11:09 AM.
12-30-2012, 02:06 AM   #10
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QuoteOriginally posted by snostorm Quote
This image is linked from Robertstech.com page:
Scott, looks like that page won't let you link.
12-30-2012, 03:36 AM   #11
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I'm at a complete loss as to how you are mounting the lens on the TC, the rear element of my 100mm is way too close to the rear to be able to let the TC front element in there????
01-02-2013, 01:26 AM   #12
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Just an update, I just went to Sigma service centre and was told that there was a problem with the contact pin. I can now set the aperture but due to the incompatibility of the pins of the TC and the lens, it cant AF. At least I can use MF, it is for macro anyway. So just to confirm again, Pentax FA 100mm 2.8 macro and Sigma 1.4x APO EX DG TC cannot AF but can set the on body aperture.
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