The notion that what is in effect a second lens, inserted between the real lens and the camera, will not detract from image quality is counter intuitive to the point where I have never seriously considered using one of these devices to extend the reach of my lens.
The lens extender is not the same thing as the extension tube that we use to magnify small objects for macro photography. Both devices maintain the electronic link between lens and camera, but the extension tube has no glass, it achieves the required magnification simply by moving the lens away from the sensor.
The Lens Extender is designed to work with Canon L series lenses and is in effect a second lens. The reason I became interested was that during the course of a landscape photography workshop I was unable to get the framing I wanted, even at the maximum zoom length of my lens. A quarter of a mile walk may have done the trick, but I would then be shooting from a completely different angle. So longer lens? Or Lens Extender? The lens extender costs approximately 30% of the price of a longer lens. That sharpened my attention.
So what’s the pay off? The lens extender loses you a full stop in maximum Aperture, so the f4 becomes an f5.6. This shouldn’t be an issue for landscape photographers who will tend to want back to front sharpness and will often opt for the lenses comfort zone – around f11. I tried some test shots with the 70-200mm lens. I discovered that autofocus was struggling, but that’s not a major issue, I tend to use manual anyway with landscape photography. There appeared to be some chromatic aberration introduced around high contrast edges, but nothing that couldn’t be addressed in post. In the viewfinder, I thought there was some vignetting, but that disappeared when I imported the images into Lightroom. As for sharpness, this is a crop from a larger photograph shot at a distance of 150 metres. At full magnification you can see the detail of the seagull sitting on the chimney. Its as sharp as it probably needs to be!
The outcome? The downside is that it is more fiddly to put on the lens extender, then the lens than it is to just swap lenses. Again that is unlikely to matter much to a landscape photographer. Some aberration is introduced, but a very small amount. I would expect considerably more actually since we’re introducing a whole extra layer of light processing before it gets anywhere near the sensor! I guess the verdict is that this is a useful tool for landscape photographers. It is not the same as having a longer lens, but it is cheaper and lighter and both of those things count.
I’ll be adding one of these to my kit. In terms of lightness, that alone earns it a place. Last year I visited China, India and Spain. And in China, I really regretted not taking a longer lens. This year I’ve already been to Spain once and have trips to India and France planned already. I don’t have the room or the strength to carry a flotilla of lenses around so until I actually invest in that longer lens, this useful piece of kit will do a good job and save my aching back!