Tamron 2.0X Teleconverter (Model TC-X20) for Select Tamron Lenses in Canon Mount

This teleconverter is advertised for the 150-600, but I think it needs to be targeted to the 70-200mm f/2.8 G2 owner instead (I have the latter). The reason is 2 stops of light is a huge issue (see below). For me, going from f/2.8 to f/5.6 is forcing me to relearn how to use the lens. But, it is still usable in all its auto focus/ image stabilization glory. If you are a 150-600 owner, you will likely be ticked off. If you have a body that only has a center focus point at f/8, my guess if you can't use AF at all. With my 70-200mm f/2.8 G2, my max aperture is still a decent f/5.6, so all my EOS 80D AF points work as usual.So, did I get my money's worth? Actually, I am still trying to figure that out. My issue is that cropping the 200mm to get the same effective magnification is usually ok, and the image quality with 400mm and no crop is only a little bit better. But I am using an APS-C sensor, so I think I have used every bit of magic this wonderful lens has in it. So far, the biggest advantage is being able to see more of the subject to use manual focus. Overall, the combo of the 70-200 and 2x tele is pretty comfortable and extremely flexible.* A 2x teleconverter provides the magnification by doubling the image circle. For verification of that concept, I set my lens up on a tripod. I used a flashlight pointed into the front of the lens, and a piece of foam board set to the same distance as the sensor. Without the 2x, I marked the light circle. Then I did the same with the 2x. I saw that the circle is doubled. So that explains why you lose 2 stops of light-- that's also why you get a reported f/5.6 aperture. The lens is actually wide open-- you can see that in the Bokeh produced (and lack of sharpness). Most modern bodies AF systems work to some extent down to f/8 max aperture. So, those with the 150-600, with max aperture of 5, the effective aperture is something smaller than f/8. That will be true for the new 100-400 as well. So folks that want to use those lenses should probably steer away from the teleconverters, and use an APS-C body.

Works great with the Tamron 70-200mm f2.8 G2 on my Canon 80D. I read all the reviews and didn't intend on using it with a 150-600mm G2, so I won't give it a bad review for that. Tamron will probably come out with an update for the TC-X20 or the 150-600mm to correct the issues people are having with this and the 1.4x on that lens. Anyhow, I felt like I got a great deal on this tele. I was reading some reviews and thought i'd check to see if there were any open box or used ones since a lot of people may be returning it due to the issues above. And I scored one for half the price and couldn't have asked for one in better condition. I only had the tele for 2 days, but it works great.I also own a Sigma 50-500mm HSM OS and it's pretty sharp at 400mm and not bad at 500mm. However, this 2x works so well I'm going to sell that BIGMA. The Tamron at 400mm is just as sharp in my opinion so far and I also have f5.6, whereas the Sigma is f6.3 at 400mm. Hopefully they work out the bugs since $400 for a quirky tele is steep in my opinion.The build quality is great, just like the 70-200mm G2 and also comes with the weather seal. It feels solid and locks snug. It also came with a nice pouch which I am using since I ran out of other neoprene pouches atm.If the fix the bugs with the big lens, I will probably pick one up and a 1.4x to go with it. But the 2x combo with my lens is a perfect smaller solution than carrying the BIGMA and Tamron lenses around.I did attach both the tele and lens to the Tap-In adapter and if I need to adjust the focus at some time I will, I can also update the firmware once one becomes available.

The extender works great.Not sure why one review says it works with a Tamron 24-70mm G2 this extender with not work with the Canon version Tamron 24-70mm G2. Not sure about the Nikon version.

I have a Canon EOS 6D Mk II and a Tamron SP 150-600mm Di VC USD G2 lens that I use primarily for astrophotography. I purchased the TC-X20 after reading the specs and researching the features on the Tamron web site. Both the specs on Amazon and the Tamron web site indicated the teleconverter was compatible with the G2 lens, and it supports the Autofocus and Vibration Compensation features. It does support VC, but not the Autofocus. I can control the lens focus with a laptop, so it beats me as to why the camera's Autofocus will not work. Since I will likely only use the teleconverter for astrophotography I will keep it, but if you need the Autofocus feature, avoid this one.

I checked Tamron's website before buying at (Amazon policy won't permit me to post the link)The website indicates that the Tamron 2.0X teleconverter (model TC-X20) is compatible with my Tamron 100-400 F/4.5-6.3 Di VC USD.When the teleconverter arrived, I attached it to my camera and, while the stabilization would activate, the auto-focus remains stuck at Manual (despite the setting on the lens). I updated the camera firmware and, using the Tamron Tap-in console, I also updated the lens firmware. There are no updates available for the teleconverter. Nothing worked.Finally, I called Tamron support and they referred me to another Tamron web site (Amazon won't let me post the link) that contradicts the product web site. My lens is not supported. It seems that every other lens and camera in the universe is supported except for my 100-400, despite what is advertised.I'm a big fan of Tamron, but this one is inexcusable.What a shame.

I'm using this converter alongside the Tamron 70-200 G2, on a Canon 70D.Autofocus still works, especially keeping aperture at 5.6 or lower on the70D, and shots so far still seem sharp even at 200mm with this converter. Not as sharp as 650mm lens perhaps but very good.