Canon EF and EFs Lenses

Welcome to Macro Photography for Beginners. This post is about the difference between Canon’s EFs and EF lenses. So if you're not a Canon user this might not be the most interesting post to read.

It will have either escaped your attention completely or kept you awake at night with wonderment, that Canon manufacture lenses for their EOS cameras in two different lenses mounts. I’m talking about the description that accompanies the lens which will either be EFs or EF. In actual fact the mount is exactly the same, but the lenses have a slightly different design.

The original EF lenses are compatible with all of Canon’s range of EOS cameras. The EFs lenses are designed to only be compatible with digital EOS cameras that use the APS-C size of sensor. Most photographers will recognise the APS-C sensor by its cropping factor (in this case 1.6x). This may all seem like irrelevant information but depending on your aspirations could leave you with lenses that you can not use. If for example you intended to upgrade to a professional specification of canon EOS digital SLR camera you would find that your EFs lenses were incompatible.

An EFs lens would not be compatible with a full sized sensor camera (for example Canon’s EOS 5D). It is for this reason that I would not recommend buying EFs lenses if you intend to upgrade to a full frame sensor in the future. However, some entry level photographers buy EFs lenses knowing that they will be compatible with semi-professional EOS cameras like the 50D. The rumour mill predicts that at some stage full frame technology will filter down through the range.

To put this into a very basic prospective the S in EF-s stands for Short Back Focus. The design of an EF-s lens allows it to protrude further into the camera. This means that the rear of the lens can get closer to the sensor than an EF lens. An EF lens is relatively flat in comparison. It is for this reason (for example) that you can not use a tele-converter with an EF-s lens. It is physically incompatible i.e. in this case they simply would not fit together. The protruding part of the EF-s lens would hit the glass of the tele-converter. (See my detailed and artistically drawn diagram - and check out the lined note paper, click to enlarge).

Image 1: Simple Diagram showing the difference between a Canon EF and EF-s lens

As stated earlier, this is worth remembering if you are considering buying a EF-s lens for a APS-C sensor camera but aspiring to upgrade to a full frame camera. However, the rumour mill (or internet as it is also known) suggests that because, unlike Nikon, Sony, and all the other known SLR brands, Canon actually manufactures their own sensor technology. It is likely that they will gradually incorporate full frame sensors into their semi-professional cameras and maybe even the entry level cameras as well. This would leave some photographers with a camera bag full of useless EF-s lenses. I’ve included a list of Canon EOS cameras by sensor size for reference.

EOS 1000D APS-C
EOS 450D/500D APS-C
EOS 40/50D APS-C
EOS 5D Full Frame
EOS 5D II Full Frame
EOS 1D III Full Frame
EOS 1Ds Full Frame

*Full Frame - no cropping or magnification

Macro Photography for Beginners
This post is not the usual fare for this website but I believe that this is useful information, considering that a popular macro lens for canon users is the Canon EF-s 60mm f2.8 Macro. To be perfectly honest, I found all this information scribbled on a scrap of paper ready for the shredder. It was probably part of another article or post that I never completed writing. So the post that you've just read was destined for the bin.

I've been very busy recently and apologise that I have not been able to respond to comments or feedback at my usual lightning pace!

Marvin Africa