I have usually used a Canon 100-400L lens for baseball, or a Sony 70-400G lens if shooting with my Sonys. Under the lights I usually shoot either a Sigma 120-300/2.8 HSM OS or a Canon 300/4 L. The Sigma 150-600C, though, is giving me results that equal or better the 100-400L in these daylight shots. I am also considering getting the new Tamron 150-600 lens, pending reviews. I was just curious if a Canon extender, specifically the canon EF 2X III, will work on the Tamron and/or Sigma lenses. Note that I currently own the Sigma 1.4x teleconverter but I'm not very happy with its IQ. sigma. Agree with the others that the RF 1.4x is an excellent addition to the bag. It's very sharp and fast-focusing, even more capable than the 1.4x iii (on the 100-400ii). I've hardly had mine off the RF 100-500, it's that good (I do mostly birding). A couple of samples from the R5 For comparison's sake: Canon EF 800mm F/5.6 USM L w/ 1.4x Teleconverter III mounted to a Canon EOS R6. Effective focal length is 1120. Shot at ISO 800 at 1/750 of a second, handheld, backlit, in The Canon 1.4x III Extender will not work on the Sigma 150-600 C or the Sigma 150-600 S The Canon 1.4x II will work on both C and S version and of course the Sigma TC-1401 1.4x. If you use the Canon 1.4x II Extender you might experience Major back focusing and slow focusing you need the best of light because you are at F9. This item Canon EF 2.0X III Telephoto Extender for Canon Super Telephoto Lenses Sigma 150-600 Mm F/5-6.3 Dg Os HSM Contemporary Lens for Canon Cameras (745101, Black) Canon EF 25 II Extension Tube for EOS Digital Cameras Canon EF 100-400mm F4.5-5.6L IS II Canon EF 70-200mm F2.8L IS II USM Canon EOS 80D Canon Extender EF 1.4x III Canon Extender EF 2x III. got the Sigma 150-600 Fully agree. I started last year with the Sigma 150-600 c, I even had the Sigma 1401 TC. Both performed pretty well, but the lens is big and heavy. I could handhold the combo, but was a pain. The lens performed better at 550 than 600. I finally moved to the RF 150-500 + RF 1.4 and the combo is amazing. Easily the best lens I have ever owned. There are a few lenses that give a similar, but slightly different, focal length range to a 150-600mm - and below are some of those which are worth considering: (Image credit: Future) 5. Canon RF 100-500mm f/4.5-7.1L IS USM. Not a 150-600mm - but a great option for Canon full-frame mirrorless. Specifications. Canon 100-400 Mk II used with Canon 1.4 Mk III Extender. I am finding that I cam cropping, sometimes heavily with the above setup because I want that “closer” image. I was considering switching to Sigma 150-600 sport or their newer telephoto, the sigma 60-600 iJCp.