Canon Extender EF

The Extender EF lenses are a group of teleconverter lenses made by Canon Inc.

These lenses are used between any compatible EF type lens, and any of the Canon EOS line of cameras.

When used with a compatible lens, such as the Canon EF 500mm f/4L IS USM they will multiply the focal length of the lens by a factor of either 1.4× or 2.0×. This will result in a focal length of 700mm or 1000mm, respectively.

Four Extender EF lenses have been available.

* 1.4×
* 1.4× IIcite web
url=http://www.canon.com/camera-museum/camera/lens/ef/data/extender/ex_ef1_4xii.html
title=Extender EF 1.4X II
work=Canon Camera Museum
author=Canon Inc.
accessdate=2008-01-11]
* 2×
* 2× IIcite web
url=http://www.canon.com/camera-museum/camera/lens/ef/data/extender/ex_ef2xii.html
title=Extender EF 2X II
work=Canon Camera Museum
author=Canon Inc.
accessdate=2008-01-11]

Technical information

While the Extender EF lenses are not designated L series lenses, they are of similar professional build quality. They are constructed with metal bayonets, and engineering plastic ends. There are no moving parts, other than the lens latch lock. Two generations of the extenders exist, the older 1.4× and 2×, plus the newer 1.4× II as well as 2× II. The newer II versions have the same optical designs as the previous I design, however Canon added weather-sealing and anti-reflective surfaces inside the extender body. The optical construction of the 1.4× versions are a of five-element design. Both 2× versions use seven elements.

Compatibility information

These Extender EF lenses can only be used with lenses that have a compatible mount. While all EF lenses have mount designs that can be used with EOS bodies, only lenses with accordant mounts can be used with the extender EF lenses. These lenses must have the clearance to accept the protruding lens on the extender, as well as 10(3 extra) electronic contacts for proper electronic communication with the extender. These extra electronic contacts are used for sending the correct aperture information to the body. When a compatible lens is used with an 1.4× or 2× extender, it will cost the lens a one stop, or two stop decline in aperture size, respectively. Autofocus speed of any used EF lens is also affected. When used with the 1.4× extender, autofocus speed is reduced to a half. When used with the 2× extender, autofocus speed is reduced to a quarter. Image stabilization may not work on lenses that are equipped with one, when used with an extender, and certain EOS bodies.

Though not specified by Canon as such, users have reported that the tilt-shift lenses in Canon's line-up can also be used with the extenderscite web
url=http://www.the-digital-picture.com/Reviews/Canon-TS-E-24mm-f-3.5-L-Tilt-Shift-Lens-Review.aspx
title=Canon TS-E 24mm f3.5L review
work=The-Digital-Picture
author=Bryan Carnathan
accessdate=2008-10-06] cite web
url=http://www.the-digital-picture.com/Reviews/Canon-TS-E-45mm-f-2.8-Tilt-Shift-Lens-Review.aspx
title=Canon TS-E 45mm f2.8 review
work=The-Digital-Picture
author=Bryan Carnathan
accessdate=2008-10-06] cite web
url=http://www.the-digital-picture.com/Reviews/Canon-TS-E-90mm-f-2.8-Tilt-Shift-Lens-Review.aspx
title=Canon TS-E 90mm f2.8 review
work=The-Digital-Picture
author=Bryan Carnathan
accessdate=2008-10-06] . However, when used with an extender, the lens will not pass on the correct aperture to the camera. The focal length stored in the EXIF data will also be incorrect.

List of compatible EF lenses

The following is a list of EF lenses that are compatible with the Extender EF lenses. Their resulting focal lengths, and apertures. Also listed is how the lens will react in terms of AF, and IS. Please look at key at bottom of chart.

† - When the Canon 180 mm f/3.5L Macro USM is used with the Extender EF 1.4×, AF will only work from 0.8m - infinity, you must focus manually from 0.48m - 0.8m.

‡ - Will only autofocus with center AF point.

¥ - TS-E lens, isn't equipped with an autofocus motor.

ee also

*Canon EOS
*Canon EF lens mount
*Canon L lens

References

* [http://software.canon-europe.com/files/documents/EF_Lens_Work_Book_11_EN.pdf EF LENS WORK III DESIGN SPECIFICATIONS & LENS MAPS]