Sigma teleconverter and lens won't focus on EOS 6D Mark II

[beckszumba]

Hi I have a canon 6D Mark ii. I just bought a 1.4 sigma teleconverter for my 150 - 600 sigma contemporary lens. I am having a hard time getting it to focus on a subject. Is this normal or is it not compatible with my camera? 

[shadowsports]

Greetings,

I have the 150-600c with TC-1401, and a 6D2.

What AF mode are you using?

What are you trying to focus on?  How far way is it?

[beckszumba]

Hiya. I’m using Spot mode. Photographing birds and usually between 5 and ten feet away.

[kvbarkley]

That might be too close. I don't know what the teleconverter does to the minimum focus distance, but that is pretty close to the minimum focus distance of the 150-600!

[MikeSowsun]

You are probably too close to the subject. The Sigma 150-600 has a minimum focus distance of 280cm = 2.8m = 9.19ft = 110in = 9′2 1/4″ ft

[shadowsports]

@beckszumba,

kvbarkley, Mike and I all believe the same.  You don't need your TC to shoot birds 5-10 ft away, (honestly even 20) with a 150~600 FL.

This is why my first 2 questions were AF mode and distance.  Also recommend you get a good tripod or stabilizer for birding.  Disable IS    

The Sigma C is an excellent match for the 6D2.  You also want to be sure you are running FW 2.00 at minimum.

Ver.2.00

2018.09.10

• It has ensured compatibility with Canon’s in-camera Lens Aberration Correction function, which enables correction matching the optical characteristics of the attached lens. *
• It has corrected the phenomenon that abnormal images appear or operation errors occur when Canon’s in-camera Lens Aberration Correction function is enabled.
• It has improved the AF speed in certain combinations with some cameras.

* Compatible cameras:
EOS-1D X mark II, EOS 5Ds, EOS 5Ds R, EOS 5D mark IV, EOS 6D mark II, EOS 80D, EOS 8000D(EOS Rebel T6s, EOS 760D), EOS 9000D(EOS 77D) , EOS Kiss x8i(EOS Rebel T6i, EOS 750D), EOS Kiss x9i(EOS Rebel T7i, EOS 800D), EOS Kiss x9(EOS Rebel SL2, EOS 200D)

Tweaks to AF performance were introduced beginning with this version.  v2.03 is latest. It won't hurt to go straight to it if you are running an older version.

[beckszumba]

Thank you. I just updated my lens. Do I also need to update my camera firmware? 

[Waddizzle]

Do not use the teleconverter for this scenario.

Any distance to the subject that is under 10 feet, or 3 meters, will be too close.  This is assuming that you are zoomed all the down to 150mm without a teleconverter.  If you are zoomed all the way out to 600mm, then I would expect that minimum focus distance of 3 meters to increase. How much it might increase is not specified by Sigma.

I am uncertain if Spot AF is even compatible with the teleconverter and this lens.  I recommend using a single focus point.  The center AF point. 

Finally, check the focus limiter switch on the lens. 

[shadowsports]

The camera will function just fine without a FW update, but at this point there is no reason not to update the camera to 1.1.1.  (released in 2021) It contains all of the previously released updates.  1.0.4 was important functionally, I skipped 1.0.5 which corrected a vulnerability, but someone had to be physically connected to exploit.

v1.1.0 (also meaningful) improved connectivity with NFC devices and Camera Connect.  The latest, v1.1.1 didn't add any functionality, but improved menu navigation and language display.  Might as well grab it.  It may very well be one of the 6D2's last updates.  

[ebiggs1]

" I just bought a 1.4 sigma teleconverter for my 150 - 600 sigma contemporary lens. "

As others have advised to stop using the tel-con if you are that close to your subjects, but I will further that advise and say ditch the tel-con completely. Stop using it period. I have one. Can you get good photos with it? Yeah, you can but the penalty it brings is not worth it. A much better approach if you are not doing so now is to get a post editor. Canon offers you DPP4 free of cost and it will enhance your birds shots a thousand time better than that tel-con does or can.

What are the drawbacks the tel-con brings?  First it reduces your aperture by a stop at each focal length (FL). Second it reduces the lens IQ by some amount. The first one means you will need more light to properly expose in a situation where you already want a faster shutter speed (SS). The second hits the lens IQ and that is a problem if you intend on cropping the image some or a lot.

Here is what I suggest you do.

Change your file format to large Raw. Don't use jpeg anymore or ever again. U/l the Raw files in DPP4 which will be seamless and actually no different than most likely what you do currently. The amount of editing ability is greatly enhanced on a Raw file than on a jpeg. You can go as far with it or as little as you wish.

Use Av mode never use, " I’m using Spot mode.". Probably try f8 as a starting point.  You can set upper and lower SS. Set ISO to Auto ISO and set upper and lower limits for it. Use One Shot focus and just the center focus point. Do not use Ai-servo. This is the set up I use for birding

If the birds are sitting still or moving slightly a tripod may help but if they are moving about or flying the tripod will not help. In fact it will make it nearly impossible to get good bird shots. A monopod might be a good idea to try.  I hear advice to turn off IS, or OS in the case of a Sigma lens, but I have never seen any difference or benefit so I leave it on all the time. And I have tested it a lot!

Hey, let me know if this helps you. You can come back and u/l some examples.