• 1.4x telephoto extender for multiplying focal length of Canon 135mm or longer lenses
• Fits all 135mm or longer fixed focal length lenses and some 70-200mm telephoto lenses
• Preserves autofocus on any EOS camera when combined with f/4 or faster lens
• Weather-resistant construction and improved anti-reflective surfaces in the barrel
• Measures 2.9 inches in diameter and 1.1 inches long; weighs 7.8 ounces

Multiply the focal length of your 135mm or longer lens by 1.4x without sacrificing image quality with the Canon EF 1.4x II extender. Optically superb, the lens fits all Canon 135mm fixed focal length lenses (except the 135mm f/2.8 Softfocus lens), along with the EF 70-200mm f/2.8L, 70-200mm f/2.8L, 70-200mm f/4.0L, 70-200mm f/4.0L IS USM, and 100-400mm f/4.5-5.6L IS zoom lenses. In addition, the extender doesn't sacrifice your autofocus on any EOS camera as long as it's combined with a lens having an f/4 or faster maximum aperture (the extender reduces the effective aperture by one f-stop). Best of all, this version maintains the outstanding optics of the earlier incarnation, but adds a weather-resistant construction and improved anti-reflective surfaces in the barrel. The EF 1.4x II extender, which measures 2.9 inches in diameter and 1.1 inches long, weighs 7.8 ounces.

Attaching this high performance Extender to a 135mm or longer lens, or to the EF 70-200mm f/2.8L boosts the focal length by 1.4 times. With five elements in four lens groups, it preserves the prime lens' image quality.

I have the 2x converter but found this to be a bit soft and certainly slow on autofocus with both my 100-400 and 70-200f2.8 lenses. A fellow enthusiast told me to try this converter and I am so glad I took his advice. I used it with my 70-200 at the local airshow and was amazed at some of the shots I got even into the sun [you dont get an option usually at an airshow] The focussing was fast and accurate. Follow the instructions though about attaching this as regards sequence and switch the camera power off whilst adding it otherwise I have found the auto focus doesnt pick up so well if you add it with power on.

I just got this, but was happy to see that it is "L" build. That is, metal and matches the color/style of the 70-200mm f/2.8L IS USM.

No tests yet to comapre before/after. Does anyone know pf a good test pattern to download and print that has progressively smaller lines, like a "bull's eye" style pattern for testing lens sharpness? I see a lot of subjective evaluations, but would liek to see some pictures at a fixed length that actually demostrate the differences.

I'll look for something like this and update this review with pictures once I do.

Oh, and my f/2.8L is a f/4L with this thing attached.

Thanks, Canon!

There no words to say then GOOD
It very help with the zoom lens.

Got this to go with my 70-200L 2.8 IS lens which this is perfect for my shooting needs. Gives the added extension to the lens on my 5D and still maintains the image stabilizing and AF function. Canon did design this to fit only specific Canon lenses.
I tried it on my Sigma 50-500 and the outerbarrel of the TC will not fit inside of the Sigma.
Otherwise the TC was pretty sharp at least my copy is .

It comes with a little bag to store it in the gadget bag and as I said its a little heavy for its little size, yet it doesnt become a burden to carry at all. I am using it with a 70-200 f4L IS and the size of the combined lens looks quite long on a rebel XTi and of course draws attention to it. I dont notice any quaility decrease (on the pictures) when used with this lens, but anyway, im not using any lab equipment or pixel picking to really test that. The build feels solid and it fixes well to the other lens as if it becomes a part of it, I think thats what the intention is of course. The color of this extender is exactly the same as the 70-200 f4L IS which is not white but rather grayish, they both look beautiful together !

I highly recommend it since it does make quite a difference and overall it is a professional and very well developed pice of equipment. Im actually thinking on also having the 2x later on to achieve the 640mm with my 70-200L and a small sensor such as the XTi or the 40D.