Canon's EF Extenders . Without an Extender attached, the Canon 200mm ƒ/2.8 II USM lens shows very good results at ƒ/2.8, becoming almost tack-sharp at ƒ/4 through to ƒ/11.

Canon lens extenders were designed in the era of film, making them fully compatible with full-frame, APS-H and APS-C EOS digital cameras. The trade-off to the 40% extended range of the extender is

The lens and extender combo can always be used in manual focus mode. Meanwhile with the Canon Extender EF 1.4x II you can easly extend the focal length of compatible Canon L Series with very little degradation in the final digital picture. My advise is to go for the 1.4 extender.
The Canon EF 1.4x II Extender is an easy and very affordable way to noticeably extend the reach (focal length) of compatible Canon L Series lenses (and a few additional lenses). The Canon EF 1.4x II Extender mounts between the compatible lens and body, and multiplies the focal length settings of your lens by 1.4x.
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.
Extending the effective focal length of select Sony E-mount telephoto lenses, the FE 1.4x Teleconverter increases the lens's magnification by 1.4x for a narrower field of view. The dedicated design maintains full communication between the lens and E-mount mirrorless cameras, including auto-exposure metering, autofocus, and Optical SteadyShot

The difference between the current Canon EF Extenders, EF 1.4 x II and the EF 2 x II, and the previous versions. Bodies that may require exposure adjustment when using extenders with the EF 500 and 600mm f/4 IS USM lens

Note: Kenko TELEPLUS PRO300 DGX teleconverters are compatible with only proprietary lenses (Nikon and Canon) and Tokina lenses (except Tokina AT-X 70-200 F4 FX VCM-S and opera 50mm F1.4 FF Nikon mount). Other manufacturers' lens and camera models, or side-party adapters, are not supported.
Canon E-72II Lens Cap. $13.50. $15.00. Buy Canon Extender EF 1.4X III features EF Mount Teleconverter, 1.4x Magnification Factor, Microcomputer Controlled, Communication Between Lens & Camera, Spectra Coating Reduces Ghosting/ Flare, Protective Fluorine Coating, Dust and Water Resistant, C.

Even with a 1.4X TC III its image quality is on par with the best Sigma and Tamron have to offer, and without a TC its image quality is unmatched, except by the EF 70-200 f/2.8L IS II. Add to that a short minimum focus distance and the EF 100-400 L IS II is the best lens in the 100-560mm range.

The important factor governing the use of the Extender EF 1.4X III is actually the lens you are using with it, not the camera. Extenders will only work with certain fixed focal length L-SERIES lenses of 135mm or great, and these select zoom lenses: 1 EF 70-200mm f/2.8L USM 2 EF 70-200mm f/2.8L IS USM 3 EF 70-200mm f/2.8L IS USM II 4 EF 70-200mm

I have the Canon 100-400 version II, Canon 400 5.6L Canon RF 800mm F-11 and the Sigma 150-600mm Sport along with both version III Canon teleconverters. My preferred R5 setup would be my Sigma 150-600mm with the Canon 1.4x III converter giving me a 840mm F-9 setup. Bob 420-700mm f/8-10. 600-1,000mm f/11-14. Canon RF 70-200mm f/2.8 IS USM. Not compatible. Not compatible. Canon RF 28-70mm F2 L USM. Not compatible. Not compatible. While it’s obviously disappointing that the 70-200mm won’t work at all with the teleconverters, and the 100-500mm only half works, both the 600mm and 800mm primes are fully EXTENDER EF1.4x II. エクステンダーとは、カメラボディと撮影レンズの間に装着して焦点距離を延長するためのアダプターレンズである。. 装着レンズの高い光学性能を維持しながら“エクステンダーEF1.4×II”は1.4倍に、また“エクステンダーEF2×II”は2倍に
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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 This page provides information on the compatibility of TAMRON and photographic camera lenses with camera bodies. Di II Lenses 18-270mm F/3.5-6.3 Di II VC PZD I traded in my Tamron 150-600 and bought a 100-400mm II. The Tamron at 600mm and f/8 on the 5DIII is as sharp at the centre as the 100-400 II at 560mm with a 1.4xTC. It is true that at f/6.3 the Tamron is a bit soft but at f/8 it is very sharp throughout its whole range and supersharp from 300-400mm.

A good 1.4x teleconverter, when used with a Canon L 300mm f/2.8 or 300mm f/4, can outperform a good (but not great) 400mm telephoto such as the Sigma APO (not the APO macro version) lens. The 300 + 1.4 TC combination also roughly equals the performance of a 400mm Canon L f/5.6 lens. FF is of course more expensive, but the price differential

The T CINE Speed Booster ULTRA 0.71x Adapter from Metabones allows a Canon EF-mount lens to be mounted onto a camera with a FUJIFILM X-mount. The adapter's optics maximize the connected lens's apparent angle of view by a factor of 0.71x while providing a one-stop increase for the camera over the lens's aperture range. More Details.
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