there is still a big question running in my mind about this conclusion: How can you modify the extender glass construction and claim to have an impact on some lenses but not others of the same focal? By the way, where are those \"controlled tests\" ?
I understand for the focus speed as it is related to new electronics, but changing your glass recipe must not have an impact on all lenses? This questioning has nothing to do with my observation as they were not done in a perfect environment and process. But still, that keeps me thinking...
JD
Please forget if I don\'t follow your thoughts exactly but I believe you misunderstood the Canon\'s words regarding the design of the new teleconverters. If I recall correctly, they didn\'t claim that new design will have a different impact depending on the lens used, it was regarding the new microchip that helps with AF.
Also they said nothing about the (faster) focus speed but focus \"precision\" - and this varies depending on the lens used with the new teleconverters.
As for the AF speed, Canon wrote in their press release, that new III teleconverters, the same as II version, will decrease AF speed by:
- 50% - 1.4x
- 75% - 2x
Hi Kosin,
This is what I read:
From the text included in Canon press release and this is not really related to the focus:
\"Allowing professional photographers to shoot distant subjects without having to carry a number of heavy lenses with them, these new extenders ensure there is no compromise on image quality. The Extender EF 1.4x III features three lens groups of seven elements, and the Extender EF 2x III features three groups of nine elements, ensuring improved optical performance.\"
Extracted from Canon Paper:
\"Image Quality
There are two significant improvements related to image quality when using the new Series III Extenders with the new IS II super-telephoto lenses: Anomalous dispersion glass elements are used in both new extenders to effectively reduce chromatic aberration to the greatest possible extent. This results in higher resolution and contrast, especially when the new extenders are used with IS II super-telephoto lenses. \"
I understand there are some better resolution and contrast and chromatic aberration.
JD
Dec 28, 2010 at 01:45 PM
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