Lens: Focal Length & Maximum Aperture: EF1.4X III: EF2X III: EF 135mm f/2L USM: 189mm f/2.8:

72.0x 52.7. Weight (g) 325. Designed to extend a lenses focal length by a factor of 2x, the redesigned Canon Extender EF 2X III delivers optical performance on par with the finest Canon super telephoto lenses. It features a built-in microcomputer for seamless communication among camera body, lens and extender, features careful lens placement

You can't use a Canon extender with any EF-S lens, they aren't incompatible - not all EF lenses will work either - extenders are designed only for specific L-series EF lenses (and a couple of DO ones), one of the reasons they are white. For example, the excellent EF 70-300L lens is not compatible either. The EF 75-300 lens won't work either and

Anybody tried out the Canon EF 2x III Extender with the EF 70-200mm f/2.8L IS II USM? It works well and the combination replaced the 400/5.6 for me. Wide open at 400mm the prime is a little bit better. Stopped down 2/3 stop the zoom with TC is equally good in my experience and IS is a huge advantage of the zoom combo.

1. 2X III works really well and maintain a reasonable sharpness only on Superteles, 100-400 II and on on 70-200 II and unfortunately not included the 100-400 I. It's a waste of money. kingfishers are one of the skittish creatures, it posts a challenge even with 600mm + 2x. If you use a 2x with 400, you may find the distance not usable as you
Here is a look at the Canon EF 70-300 L with EF 2x III Extender ISO 12233 image quality. Wide open, the results with the 2x installed are remarkably close to the performance of the 1.4x III, but more sharpness/contrast degradation is apparent - especially in the center of the frame. The 1.4x III takes a wide lead in the image quality race when
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canon ef 2x iii extender lens compatibility