Taping pins on Kenko 1.4x TC does not work

I placed this message in the TC sticky, but it did not attract any attention. Maybe a new thread is needed, but still my apology for the duplication.

I just bought a Kenko 1.4x TC, with the idea of trying to tape the three pins to allow auto focusing at F/8 on the 70D. No such luck - as soon as I tape the pins the camera immediately automatically switches into manual focus.

But I just thought: I taped the pins on the camera side of the TC, where they are flat. Maybe I should have tried to tape the pins on the lens side? Or should it make any difference?

Interesting to notice that I used the TC with a Sigma 120-400 f/4.5-5.6. If I do not tape the pins, the AF works until about 300mm, way after the F stop reaches 8. I guess more testing will be done over the weekend.

Lbsimon wrote in post #17007071
I placed this message in the TC sticky, but it did not attract any attention. Maybe a new thread is needed, but still my apology for the duplication.

I just bought a Kenko 1.4x TC, with the idea of trying to tape the three pins to allow auto focusing at F/8 on the 70D. No such luck - as soon as I tape the pins the camera immediately automatically switches into manual focus.

But I just thought: I taped the pins on the camera side of the TC, where they are flat. Maybe I should have tried to tape the pins on the lens side? Or should it make any difference?

Interesting to notice that I used the TC with a Sigma 120-400 f/4.5-5.6. If I do not tape the pins, the AF works until about 300mm, way after the F stop reaches 8. I guess more testing will be done over the weekend.

I don't quite understand what this means. Are you saying just that the camera won't focus?

runninmann wrote in post #17007229
I don't quite understand what this means. Are you saying just that the camera won't focus?

Correct, the camera won't even try to focus, as if the lens is switched to manual focus.

The side to tape the pins and the number of pins taped makes a difference. Here is a link with pictures.

When I tried my Kenko 1.4X (or 2X) with my Sigma 150-500mm f/5-6.3 it worked. It hunted a ton (IQ very so so definitely needs stopped down), and needed lots of light but it worked. I never liked the effect and on my lens in IQ and especially AF speed and accuracy. (I've thought people said it is the same for the Canon 100-400, so probably the same on your Sigma 120-400.)

My understanding is it should AF for the full range. For instance my Sigma 10-20mm f/4-5.6 will AF the entire range. (Some will ask why on this lens? It will allow AF on a FF camera with decent IQ and AF with little no vignetting for an equivalent FOV 14-28mm f/5.6-8 lens - the entire range.)

Do you have the new Kenko with the X in the name? (ex. kenko teleplus pro 300 dgx) These have new circuitry. That may affect it, but I don't really know as I have the older ones (without the X).

Hope something here helps!

Thanks Jim, the picture proved to me once again that I should never assume anything. I read so many time about taping three pins, that I thought people were talking about those three that are a little separate from the rest. I was wrong!

I know that it should work only at good lighting, so I will only be able to try it over the weekend. And no, it is not a new version. But the price was low enough for me to decide that even I have to get rid of it, I will lose very little money in the experiment. I have a Canon 1.4x II to use with the 70-200 F4, but it does not work with the Sigmas.

I've taped the pins several times on my 100-400. Always taped the lens side but I wouldn't think it would make a difference. The whole point is to break electrical contact so the lens does not report. One thing to keep in mind is that at the very long focal lengths it is very hard to hold the lens steady and keep a good contrast edge inside the focus area. If the edge is lost the lens can hunt. These days I have much better success focusing using live view instead zoomed in 10x.

gjl711 wrote in post #17007320
I've taped the pins several times on my 100-400. Always taped the lens side but I wouldn't think it would make a difference. The whole point is to break electrical contact so the lens does not report. One thing to keep in mind is that at the very long focal lengths it is very hard to hold the lens steady and keep a good contrast edge inside the focus area. If the edge is lost the lens can hunt. These days I have much better success focusing using live view instead zoomed in 10x.

I think he was taping the wrong side of the pins. That is what I mean when I say it matter the side to tape the pins.

I agree separating the contacts is all that should be needed. BUT the specific contact terminals does make a difference. Again that is where I think the OP made a mistake.

I too always taped the lens side also (for the short time I'd did this), as I did not want the tape (with adhesive) somehow ending up inside my camera body.

Again I just decided that was easier and more efficient/less frustrating (especially since I used to do it with older film bodies - albeit with better focusing screens) to manually focus with the TC-lens combination, than taping and hoping for good AF.

Agree, shooting long lens does require some practice in selecting the area to focus on, and the IS is really big help here. I have been shooting 300 and 400 mm for a while, so I learned it. However, mostly I shoot hand held. Holding a heavy camera/lens set trying to focus with the back display does not sound easy!

jimewall wrote in post #17007352
I think he was taping the wrong side of the pins. That is what I mean when I say it matter the side to tape the pins.

True. There are 7 + 3 pins. In my ignorance I was taping the set of three that are located separately.

jimewall wrote in post #17007352
Again I just decided that was easier and more efficient/less frustrating (especially since I used to do it with older film bodies - albeit with better focusing screens) to manually focus with the TC-lens combination, than taping and hoping for good AF.

I am with you on that too. I have been shooting since 1963 (my first camera is my avatar), so manual focus is nothing new or difficult to me.

More experimenting, and more results.

First, I was incorrect stating that there were 7 + 3 pins. The Sigma 120-400, as well as a couple of my Canon lenses have 5 + 3. Some othe Canons and Sigmas have 8 + 3. The Sigma 120-400 that I bought the TC for has 5 + 3, and taping three pins throws the lens into the manual focus mode, meaning that the top display of my 70D says "M Focus".

Any help?

Try using the TC on the lens without the tape. Let us know what happens.

Actually, I did. Surprisingly, it auto-focuses at F 8. Of course, only on well lit and contrasty objects, otherwise it hunts a lot.

What I did not like was that unlike the 70-200L and a Canon 1.4x TC, the 70D AF micro-adjustment does not see the TC. It shows only a naked 120-400 lens. The lens is already MA'd to +11, with the TC it needs 0, but that means that I have to do the AFMA every time I attach or remove the TC.

I will probably use it only for manual focus.

I don't have microadjust, but just an idea: how about setting up the extender+120-400 combination under "all by the same amount", and the other lenses under '"adjust by lens"?
Yes, you'll have to dive into the menu once in a while, but you won't have to recalibrate every time.
I'm assuming the camera doesn't throw away Lens specs if you switch micro off or to "all for one". I have no micro on my camera so can't test.

Lbsimon wrote in post #17010386
Actually, I did. Surprisingly, it auto-focuses at F 8. Of course, only on well lit and contrasty objects, otherwise it hunts a lot.

What I did not like was that unlike the 70-200L and a Canon 1.4x TC, the 70D AF micro-adjustment does not see the TC. It shows only a naked 120-400 lens. The lens is already MA'd to +11, with the TC it needs 0, but that means that I have to do the AFMA every time I attach or remove the TC.

I will probably use it only for manual focus.

I think the reporting only works with the lenses with 11 total pins (8+3), so your TC is not reporting with those that have a total of only 8 pins (5+3).

Unless you have a TC that has only a total of 8 pins and not 11 pins. That (I think) is what they call a non-reporting TC. (If so) You shouldn't tape any pins on the non-reporting TC, because they are all needed for SS, aperture, and AF (plus there is no reason to, they are non reporting).

Please let me know if your TC has the 8 or 11 pins. (Because) The confusing part would be is if you have a reporting TC, why it would go to manual if you taped the (correct) three pins. Since doing so should not do anything to the connections (because they are technically not connecting to anything). NOTE - It also does not explain why with the TC (no tape) that about 300mm you lose AF.

I think you hit it on the nail - by your description the TC is non-reporting, it only has 5+3 pins. The lens does AF, but not realibly. Unfortunately due to storm Arthur I cannot do any testing today, will have to wait until tomorrow when the weather is good.

I need to play more with it. So far I did not like the sharpness unless I change the MA, but this is not critical.

I bought the TC just to try, I knew there will be issues that may not be worth solving. But the price was right, and if it does not work with my Sigma, I will just sell it.