This appears to be a direct knockoff of the Canon 2.0x III Extender which costs 2.5x as much. I tested this against the Kenko 2x Pro 300 teleconverter (which is one of the best) and by comparison this has better corner sharpness and much reduced chromatic aberrations.
If you used a 1.4x extender then the 100-400 f/4-5.6 becomes a 140-560mm f/5.6-8 lens and that WILL work becuase the wide-open apertures are f/8 or lower for every focal length available. The 2x extender must not be used with any with a focal ratio higher than f/4.
I purchased a Canon Extender EF 2X III but it does not fit the lens. Stack Exchange Network Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Canon EF 100-400mm f/4.5-5.6L IS II USM Lens $2100. Canon EF 300mm f/4L IS USM Lens $1350. Canon EF 400mm f/5.6L USM Lens $1150. Canon Extender EF 1.4X III $425 . Prices are off the top of my heard but I believe they are pretty close. There might be rebates I don't know about. There is always used sources and the Canon refurb store.
Lens Construction: 6 Elements in 5 Groups. Teleconverter works with select Sigma lenses on Canon Digital SLR camera bodies only. Increases the minimum and maximum focal length by the power of 2.0x. Multi layer lens coating reduces flare and ghosting.
The 2x Extender III has some useful implications in macro work, offering an extra 100% magnification without sacrificing the minimum close-focusing distance; in the case of the 200mm ƒ/2.8L II
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canon extender ef 2x iii compatibility
