Canon 25mm Extension Tube II (EF 25) Review

The Canon EF 25mm Extension Tube II is used to allow a lens to focus closer than it does natively. This is accomplished by moving the lens 25mm farther away from the camera body's film plane or digital sensor by fitting between the camera body and the lens.

The end result of focusing closer is a larger magnification. A rough rule of thumb to use for the increased magnification is ...

Additional Magnification = (Extension Tube Length)/(Lens Focal Length)

Based on this rough rule, the Canon EF 25mm Extension Tube II put between the camera body and a Canon EF 50mm f/1.4 USM Lens will result in a .5 magnification gain (25mm divided by 50mm).

Close-up lenses such as the Canon 500D Close-Up Lens result in higher magnification when used with longer telephoto lens but shorter focal length lenses result in higher magnification when used with extension tubes.

Not only is minimum focus distance reduced, but maximum focus distance is reduced as well when using the Canon EF 25mm Extension Tube II. While not welcomed, this is part of the optical change made by the extension tube. This maximum focus distance can be reduced dramatically in some longer focal length lenses. For example, the Canon EF 300mm f/2.8 L IS Lens focuses from 5.5' to 12.2' with the Canon EF 25mm Extension Tube II installed.

Another downside to extension tubes is corner vignetting introduced on Full Frame camera body images.

The Canon EF 25mm Extension Tube II is updated to be fully compatible with Canon Digital EF-S lenses, as well as standard photo EF and TS-E lenses. Autofocus and auto exposure are maintained when using these compatible lenses. There is a bit of light lost when using the Canon EF 25mm Extension Tube II. Functioning auto exposure will take care of correcting the exposure for you.

There is also a slight degradation in image quality as the enlargement process also enlarges any distortions in the lens.

A white-index mark is provided for Canon EF-S lens installation alignment and a red mark is provided for Canon EF lens installation alignment.

Canon Extender and 25mm Extension Tube Comparison Picture

The Canon EF 25mm Extension Tube II (above right) is similar in size to the Canon EF Extender 1.4x (above left).

Kenko and other brand extension tubes are available for less money. Since extension tubes have no optics inside, Canon air is no better than Kenko air. The Canon has a few niceties such as the an included storage pouch, nicer caps and a nicer textured finish. There is something psychologically nice about the matching "Canon" label as well.

The Canon EF 25mm Extension Tube II is recommended for lenses with a focal length of 50mm and up For example, the Canon EF-S 18-55mm Lens should be used only at its mid and long focal lengths with the Canon EF 25mm Extension Tube II installed.

The Canon EF 25mm Extension Tube II is commonly used for macro photography. When evaluating the Canon EF 25mm Extension Tube II, I needed to make the Canon EF 300mm f/2.8 L IS Lens focus closer than its long native minimum focusing distance - more like the Canon EF 300mm f/4 L IS Lens. The Canon EF 25mm Extension Tube II does the job well, but I still like a true macro lens such as the Canon EF 100mm f/2.8 USM Macro Lens or the Canon EF 180mm f/3.5 L USM Macro Lens best.

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