(6 votes, average: 4.67 out of 5)

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All of the images were shot using F8, RAW, tripod, remote, mirror lockup using a Rebel XT and a Canon 300 F4 IS L. Each image has had zero color or contrast processing, but they have each had a level 4 sharpening done in DPP.

The Canon is $290 retail, and the Kenko is $190 retail. Please click on the thumbnails for the full images.

The first examples were done using manual focus.

Crops:

Things look pretty even when using manual focus at F8. Let’s check out the autofocus results using one shot AF:

100% Crops:

I took many test examples, and with this specific setup, it appears the Canon 1.4x II delivers much better autofocus results. Your mileage may vary based on your specific setup. Why is the Canon showing superior autofocus results over the Kenko? I originally bought the Canon 1.4x II to find out if it was the Kenko TC, my camera or my lens that was causing the autofocus problems with the Kenko. I even had the Kenko sent in to THK for evaluation, and they reported it’s 100% within working specification.

What’s interesting is that the Kenko and Canon have the same IQ when using manual focus, but not even close when using autofocus. Is this because of the XT’s outdated autofocus? Who knows. I did notice the Canon 1.4x II is a touch slower than with the Kenko 1.4x. Perhaps this results in more accurate results.

Some other observations:

The Canon feels alot heftier and more solid. Mounting to the camera and lenses is easier.
The Kenko can work on many other lenses, the Canon can only work on L telephotos.

I’m not quite sure what my angle of action is going to be at this point. Perhaps I should stick with my Kenko 1.4x and try it with the 40D which is purported to have a much better AF system than the XT. But if the Canon 1.4x II focuses better with the XT, won’t that also apply to the 40D? It seems those interested in more accurate AF results may put more stock in to the Canon 1.4x II. The Canon is about $100 more than the Kenko in the states. The loss of versatility, the extra cost and the samey IQ really make we want to return the Canon 1.4x II. However, if it’s going to be giving superior AF results, isn’t that what you want on your lens when it’s all said and done? Versatility doesn’t mean much when you’re losing potential keepers.

I’m leaning to keeping the Kenko and trying it with a 40D.

Bonus images using manual focus, F8, level 4 sharpening in DPP, no color or contrast adjustments: