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New Contributor
Posts: 1
Registered: ‎11-15-2019


recently purchased a EFS 18-135 lens, but it do not fit my EOS 5D Mark III . However, 28-135 ultrasonic len fitted. What type of extender do I need?  Thanks

Esteemed Contributor
Posts: 4,651
Registered: ‎02-17-2016

Re: Extender

[ Edited ]

None. EF-S lenses are not compatible with EF mounts. Return the lens. EF-S lenses are optimised for the smaller image circle of the APS-C sensor, even if you could get the lens to fit, it would vignette something fierce.

Posts: 13,794
Registered: ‎12-07-2012

Re: Extender

A couple thoughts come to my mind. You have a relatively expensive camera yet you don't know enough about it to know what lens it uses? Then you think you need an extender to make it work?

EOS 1DX and 1D Mk IV and several lenses!
Reputable Contributor
Posts: 948
Registered: ‎12-24-2013

Re: Extender

[ Edited ]

Why do you want to use an extender with your 28-135mm ?


A 1.4x teleconverter will turn your 28-135 into a 39-189mm. A2x extender will turn your 28-135 into 56-270mm.  If you want a longer focal length you will be disappointed in the results. The images will not be sharp, and the Auto Focus will be severely affected or not work at all.


Teleconverters or “extenders” work best when used with fast aperture longer telephoto prime lenses.  Canon extenders will not physically fit the 28-135 due to the extended front element on the Canon extender, and third party teleconverters will produce poor images.



Mike Sowsun
80D, 5D Mk III
Posts: 11,422
Registered: ‎08-13-2015

Re: Extender

[ Edited ]

Check out this video from the Canon YouTube channel.  It is part of series of lens videos.  This one discusses lens basics. 


He describes the EF-S 18-135mm lens quite a bit.  He discusses the difference between EF, EF-S, and EF-M lens at the 6:30 mark.  Since this video was released, Canon has released another line of lenses, RF Series, which do not fit your camera, either.


[EDIT]. Canon Lens extenders are not compatible with any lens.  Extenders have compatibility lists, which can vary from one cameras to the next.  Extenders designate various lenses with a letter category.  Your camera's instruction manual tells you how the camera behaves with each type of lens letter category, because it can dramatically impact AF performance in some cases.


"Doctor told me to get out and walk, so I bought a Canon."
Reputable Contributor
Posts: 870
Registered: ‎10-18-2016

Re: Extender

[ Edited ]

@M2Treasure wrote:

recently purchased a EFS 18-135 lens, but it do not fit my EOS 5D Mark III . However, 28-135 ultrasonic len fitted. What type of extender do I need?  Thanks

Your 5D MkIII is a full-frame camera and takes ONLY EF lenses.   The EF-S 18-135mm lens is designed for APS-C bodies, i.e. those with a cropped sensor.  The design of these camera bodies is such that the mirror, being smaller, allows the lens to sit further inside the camera body and EF-S lenses take advantage of this to make the lenses cheaper (the explanation for the design of lens optics is a bit long for this post).  Bottom line:  Your EF-S 18-135 lens will not fit and shot not be attempted to fit into the full-frame body - you could damage either or both units.


The EF 28-135 IS USM lens is one of Canon's oldest and is an o.k. lens for its range - it's an old lens design (I think their first USM lens actually) and was built between 1998 and 2016.


Canon extenders fit only specific lenses designed for them and further their capabilities to meter and autofocus with lenses is specific to the lens, extender and the body that they connect to.  I recommend that you look up Canon's extender spec charts for what works with what, via this link:  HERE 


The lens optics design for a wide to moderate telephoto are not really suitable for an extender - extenders are designed for full telephoto lenses. Furthermore, you will always take a hit in terms of quality and aperture when you add an extender.  Thus a 2x extender will double the effective focal length of a lens, but you will lose 2 stops of aperture (that reduces light to the sensor to 1/4), a 1.4x extender will increase focal length by that value, but you will lose about 1.5 stops of light.  In some cases extenders will work only at f8.   Modern extenders come at a financial cost too, so you should consider reinvesting that money into a lens built for the focal range you want.  You should get better results with a dedicated telephoto lens.


It would help if you tell us what kinds of subjects you want to photograph and then we could make recommendations as to a suitable lens.

cheers Trevor

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