Canon EF extenders
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From The-Digital-Picture.com review of the Canon Extender EF 2x III
The image quality differences most easily noticed between the 2x II and the 2x III are:
Results with the Extender 2x III are overall slightly sharper than the Extender 2x II with a difference being most noticeable in the mid-frame and corner areas. The 2x II added pincushion distortion to the lens it was used with whereas the 2x version III adds slight barrel distortion.
Anomalous dispersion glass elements are used in the Series III extenders to reduce chromatic aberration and increase resolution and contrast. The Extender 2x II did not have an issue with CA and neither does the III.
The Extender 2x III has Canon’s Super Spectra coating for reduced ghosting and flare. The front and rear elements have Canon's fluorine anti-smear coating - making them very easy to clean.
Improvements in the Series III extenders promise to perform especially well on the following specific lenses.
Canon EF 300mm f/2.8 L IS II USM Lens,
Canon EF 400mm f/2.8 L IS II USM Lens,
Canon EF 500mm f/4 L IS II USM Lens and
Canon EF 600mm f/4 L IS II USM Lens.
A microcomputer integrated into the Series III Extenders promises faster autofocusing and increased AF precision when used with the Canon IS Supertelephoto Series II lenses mentioned above and (I expect) all future compatible lenses. Better optical quality is also expected.
The image quality differences most easily noticed between the 2x II and the 2x III are:
Results with the Extender 2x III are overall slightly sharper than the Extender 2x II with a difference being most noticeable in the mid-frame and corner areas. The 2x II added pincushion distortion to the lens it was used with whereas the 2x version III adds slight barrel distortion.
Anomalous dispersion glass elements are used in the Series III extenders to reduce chromatic aberration and increase resolution and contrast. The Extender 2x II did not have an issue with CA and neither does the III.
The Extender 2x III has Canon’s Super Spectra coating for reduced ghosting and flare. The front and rear elements have Canon's fluorine anti-smear coating - making them very easy to clean.
Improvements in the Series III extenders promise to perform especially well on the following specific lenses.
Canon EF 300mm f/2.8 L IS II USM Lens,
Canon EF 400mm f/2.8 L IS II USM Lens,
Canon EF 500mm f/4 L IS II USM Lens and
Canon EF 600mm f/4 L IS II USM Lens.
A microcomputer integrated into the Series III Extenders promises faster autofocusing and increased AF precision when used with the Canon IS Supertelephoto Series II lenses mentioned above and (I expect) all future compatible lenses. Better optical quality is also expected.