by Jing Wen
In order to increase the magnification ratio of my macro lens, I decided to get some extension tubes and the best value-for-money ones were the Kenko ones. Unlike teleconverters, extension tubes don’t have any lens elements inside and thus do not affect the image quality. The Kenko tubes are compatible with both EF and EF-S lenses now, and they also have electronic contacts for aperture control.
Extension tubes work by increasing the distance between the lens and the sensor. This makes the focal point closer hence increasing the magnification ratio. The drawbacks are a greater loss of light and the inability to focus at infinity.
Some sample shots with a 35mm lens and then with a 12mm extension tube. This changes the original magnification ratio of 1:6.4 (0.14x) to 1:2 (0.5x)
More sample shots with a 17-40mm at the 40mm end, and then first using 12mm, then adding 20mm, and finally adding 36mm
Finally shots with a 1:2 100mm macro lens, first without the extension tubes
Same photo above at 100% crop
Now the macro lens with all 3 extension tubes (12+20+36)
And the above image at 100% crop
The original magnification ratio of the macro lens is 1:2 (0.5x) and after the 3 extension tubes are added on, the new magnification ratio is now 1.2:1 (1.22x), going beyond life-size! Just for reference, the native magnification ratio of a 100mm non-macro lens is just 1:6.9 (0.14x) and putting all 3 extension tubes on a 100m 1:1 macro lens will bump the ratio to 1.9:1 (1.91x).
So in conclusion, Kenko extension tubes are great for anyone who doesn’t have a macro lens and is on a budget, although you’ll have to go quite close to the subjects so it may not be ideal for wildlife macro shooters.
Using the extension tubes with proper macro lenses with bring you past the 1:1 magnification but even the smallest vibrations in the ground will affect the focusing. Tripod, mirror lockup and timer are a must!