The 1.4X II tele converter is a update to Canon's earlier 1.4X TC. The mark II allows this extender to be stacked with another of Canon's extenders without having to separate the two with an extension tube. The 1.4X II is a great way to extend the reach of compatible lenses. I have used it with Canon 300mm f4 IS, which turns it into a 420mm. 4.1: 4.1: PowerShot G1 X Mark II ** See: Limitations with Canon Dual Pixel raw files in Camera Raw and Lightroom. Casio Camera. Raw image filename extension. Model Overview. Built with distance in mind, the Canon EF 1.4x II Extender offers extra zoom for that all important moment. As an added extra to the lens, it provides excellent focal range without comprising quality. It offers a perfect lightweight option to mulitiply the focal length without investing in a new lens. As mentioned, the extender won't physically fit the EF 70-300mm L f/4-5.6 IS USM II, so IMO if you are going to spring for the EF 100-400mm L f/4.5-5.6 IS USM II, I would go for the RF 100-500mm L f/4.5-7.1 IS USM. I agree with Trevor that the EF 70-300L II is a great lens. Rol Lei Nut wrote: Ended up getting the Kenko Teleplus Pro 300 AF DGX 1.4x. On a Sony A7Rii body, MC-11 adapter and Canon 70-200 4.0 IS L, 70-300 L, 100-400 II L & 100 2.8 Macro USM, AF works well (or at least as well as the lenses do without an extender). Not used extensively yet, so plenty of time for any glitches to come out. I was too lazy to find it in the Canon material, but this is from the RF 1.4x TC product page on B&H. Lens compatibility in the description: RF 100-500mm f/4.5-7.1L IS USM (can only be used within 300-500mm range) RF 600mm f/11 IS STM; RF 800mm f/11 IS STM HyVhcse.