The new Series III extenders (teleconverters) from Canon are pretty amazing for when you need that extra reach, but don't want to reach too far into your pocket to pay for it. But how do the really stack up (no pun intended) against each other, and is there really a noticeable loss in image quality like so many doomsday critics say? We used a Canon 7D camera with a Canon 70-200mm f/2.8L IS II lens for this test and these were our observations:
Construction & Durability Improvements
The extender is solidly built and there was no movement or play when affixed between the camera and lens. These new Series III extenders have 7 screws holding the mount plate together where it attaches to the camera body; an upgrade from the 4 screws used on the previous generation of extenders. For some reason, Canon only added the extra screws to the side that mounts to the camera body, not the side that mounts to the lens. We're not sure why but it does seem like reinforcing both sides of the extender would have been nice. The extenders are weather sealed so it shouldn't be a weak spot if you're shooting on a 1-series camera with full weather sealing.
The image quality was very good in our tests throughout the aperture range, something the 2.0x Series III extender was not able to achieve. The 2.0x did a decent job at maintaining sharp image quality but the 1.4x did an awesome job and you can see that in the side-by-images below. There is not the noticeable degradation in the lower aperture range (f/5.6 and f/6.3) as we saw in the 2.0x extender. Even though the 1.4x extender only causes you to lose one f-stop instead of the two stop loss you get with the 2.0x extender, we decided to test both extenders starting at the f/5.6 setting for consistency.
So is this extender usable? Absolutely. Whether or not you buy this extender will depend a lot on how much image quality you're willing to lose and how much money you're willing to spend. At $475, the 1.4x Series III extender is a very affordable alternative to buying an expensive 400mm lens that could easily cost 20 times as much money and with the relatively negligible amount of degradation, it's definitely worth considering.
TEST CAMERA: Canon 7D
TEST LENS: Canon 70-200mm f/2.8L IS II USM
*** Please keep in mind, this was a very basic test, using only one lens, one camera body, and one lens focal length (doubled with the extender to 400mm). The results will vary based on your particular camera/lens combination but this should at least give you a basic idea of how much image degradation you can expect to lose with the extender.
CLICK ON IMAGES TO ENLARGE AND SEE DETAIL