Canon Extender EF II (1.4x) (6845A004C) Lens Converter

When upgrading to Canon's 5D Mark II, the associated "full frame" sensor (35mm, un-cropped) converted all my lenses back to their "true" focal length and essentially gained in the wide angle while loosing some "reach". What's great in many ways certainly does not work in bird watchers' favor as the 300 mm lens previously converted to a respectable 480 mm (on a APS-C sensor). Out of the alternatives of (1) add Canon's new EOS 7D body to the arsenal for $1700, (2) add a new lens with 400 or 500 mm focal length for about $1600, and (3) buy a so-called Extender for $300; the lowest cost option turned out to be the immediately feasible one.  


IN A NUTSHELL

Extenders are the lightweight and cost-effective alternative to purchasing and carrying a longer focus length. This isn't alway feasible for both budget and/or travel gear. I just purchased the venerable 70-200mm f2.8L IS USM lens and wasn't ready for another big glass.

The EF 1.4x II magnifies the picture as produced by the lens by that factor and produces a mild magnification which isn't spectacular, but described lens now ranges from 70mm to 280mm (w/o and with extender). The light loss penalty is one stop and that converts the equivalent maximum aperture from f/2.8 to f/4. This is a full stop, which means half the light density reaches the sensor.

The only compatible lens I own is the EF 70-200mm f2.8L IS USM and the fabulous optics on that one are only mildly affected by the extender. (1) AF in very low light is a bit more difficult, but (2) the 5D MkII recognizes the combo correctly for light falloff and lens correction data including the maximum aperture of f/4.

It's a bit of a hassle to install or remove the extender, but nowhere close to the "inconvenience" of hauling another 100-400mm lens (for example, but not directly comparable). Picture quality isn't unaffected but quite respectable for adding more glass into the beam path. The added detail due to the added magnification is significantly better than a cropped and scaled photo via software.

Dedicated wildlife photographers will soon add a longer length lens instead of completely relying on an extender (also to avoid the los in light and some sharpness). Nevertheless, that's expensive and typically a large and heavy lens. For less demanding users, the extender is an excellent way to give your zoom a bit more reach without having to pack a big gun (most of the time).


DETAILS

Usability: [***--] It's somewhat specialized and most useful to reduce cost and/or travel weight by increasing the reach of an existing compatible lens. It's relatively quickly installed and removed and generally maintains much of the lens' picture quality. Physics dictate a light loss to 50% in the process and 40% magnification improvement aren't exactly huge. But, when needed it's a convenient solution.

Compatibility: [***--] Unlike some other extenders, Canon's own design is relatively exclusive to a few lenses (above 135mm and mentioned zoom). This may be a disadvantage, but not a huge problem for me as the 24-105mm lens is already covered by the 70-200mm lens and my 100mm macro lens doesn't need to be a 140mm lens for my macros (though occasionally it would be nice). For added macro magnification, so-called expansion tubes like the EF12 allow greater magnification by moving closer (which would be technically outside the lens' ability to focus).

Picture: [****-] I already mentioned that picture quality is mildly affected. That's not unexpected and the EF1.4x II does a good job in keeping distortions and internal reflections to a minimum. The light loss forces the use of a tripod sooner that the lens typically suggests, but that's okay for static objects. Moving objects can only be compensated for with an increase in ISO sensitivity, if your camera supports the needed range. Bokeh and glare are well preserved from the lens, which is a bit expected since bokeh is mostly due to the aperture and glare is reduced by the new AR coating in the Mark II of the 1.4x extender.

Note: The 1.4x magnification translates into half the light (-1 f/stop) since the light density is a direct function of the imaging area (a circle). The extender effectively magnifies the picture produced by the lens and crops it back by 40% which the sensor perceives as magnification. Since there is a finite amount of light transmitted to the light, this is the reference for the extender which then takes the light and as mentioned magnifies and crops to use only 60% of the original stretched over the imaging circle. Hence it's the half the light density. (If you want to do the math just verify that diameter of 1 is half the area of a diameter of 1.4, and cutting the 1.4 circle back to 1 as done by the sensor basically removes half the area.)

AF / IS: [****-] Depending on the camera/lens combination, the AF system in most Canon cameras other than the 1D series is limited to f/6.3 as the smallest wide open aperture it supports. Certainly a f/2.8 lens converts to f/4 and that well within the capabilities of virtually all Canon EOS cameras. It's more difficult to use the extender with the 100-400mm f4.5-5.6L since the camera will force the user to manual focus (although there a ways to trick the camera which works fine if there's enough light to work with). The IS functionality is fully maintained and I cannot subjectively determine a difference in stabilization between with and without extender (considering that the 280mm are a bit more demanding anyway).

Durability: [****-] The EF 1.4x II extender is built to the same specs as Canon's "L" lenses which includes dust and weather seals. The side protruding into the lens is coated with a flexible elastomer to not scratch lenses in case you try to mate this extender to an incompatible lens (i.e. 24-105mm). The Beige design blends in nicely with Canon's line of professional lenses. The fit of the EF bayonet is tight due to the seals but in my case with slightly more movement than the EF12 tube. That does not appear to have any impact under normal use unless you're trying to mount a heavy lens via the camera's tripod mount (which is generally not recommended anyway).

Value: [*****] At $300 it's not a cheap extension for occasional long range photography, but it beats the expense of a longer zoom and it's a lot smaller too. The 1.4x magnification isn't a whole lot and with today's pixel densities one can easily simply crop. Nevertheless, for FF cameras like Canon's 5D it's a welcome gain since the typical available lenses (up to 200mm or 300mm) don't offer the same magnification as they do on the APS sensors (1.6x crop).


© 2009, theuerkorn