Canon mounts, EF and EF-S and “L” explained

There are still a lot of people out there who don’t really know what EF, EF-S and L is all about. In this post I will try to clarify exactly what this is all about.

Plastic versus metal mount

Most Canon lenses feature a metal mount. In order to make lenses cheaper, some lenses have plastic mounts like the Canon EF 50mm f/1.8 II:

Plastic mount of the Canon EF 50mm f/1.8 II lens

There is no real downside to a plastic mount in regards to optical performance of a lens. That said, it may be obvious to you that lenses with a plastic mount are generally cheaper lenses which in turn have less optical quality.


EF Lenses

EF lenses are the “full frame” lenses; the format used on analog cameras (35mm) as well. They can be recognized by having a RED dot near the mount:

Canon 100mm f/2.8 USM macro closeup. Notice the metal mount and the red “dot” which designates this is an EF-mount lens.

As cropped cameras came to the market, they initially only took EF lenses as well (like the ancient Canon D30 and no, I do not mean 30D here). This is a picture of the Canon EOS D30 without a lens attached:

Canon D30 camera (note: Not a 30D!). This is one of the first affordable digital cropped sensor cameras from Canon. Note there is only a red dot on the mount indicating this camera only takes EF lenses even though it has a cropped sensor.

As both the sensor and the mirror are smaller on cropped cameras, you can create a lens that illuminates only the smaller cropped sensor surface, plus you can allow a lens to protrude slightly into the body because you have a smaller mirror. These things combined allow you to create cheaper optical designs. They have become known as the EF-S line of lenses and are sometimes called “digital” lenses:

Closeup of the Canon EF-S 15-85mm F/3.5-5.6 iS USM lens. This lens has a white dot, indicating this is an EF-S (“digital”) lens. Note the protruding rear element which is typical for EF-S lenses (the smaller mirror of cropped cameras allow this and it simplifies lens design)

The more modern Canon cropped cameras (also known as APS-C) are able to take both EF and EF-S lenses. The Canon 30D is an example (and I think one of the first) prosumer camera body that takes the EF-S lenses as well:

Canon 30D body. Notice the red AND the white dot on the mount, indicating this body will accept both EF and EF-S lenses.

So all cameras take EF lenses, but only (most of the) cropped cameras take EF-S lenses. You can sometimes fool the system and mount EF-S on a full frame (I know sometimes the 10-22 is used on 5D’s) but in general that is risky.


L grade lenses; white and black lenses

Next to EF and EF-S lenses there are L lenses. They theoretically do not have anything to do with the EF or EF-S designation, but the L only indicates the “Luxury” lens aka better sealed, better build and better optical quality. In real life all L lenses I know of are of the EF type.

Detail of the Canon EF 100-400L IS USM lens. Note the L indication and the red stripe across the lens which Canon uses to indicate it is an L-grade lens.

The image above shows a white lens. Canon colors all of the longer L grade lenses white. But there are also black L-grade lenses. These are typically shorter (<200mm) lenses: [caption id="attachment_1136" align="aligncenter" width="400"] A shorter L-grade Canon lens, the famous EF 24-105L f/4 IS USM. Note the red lining across the front of the lens, a trademark of the Canon L-grade lenses.[/caption]


Red-and-white: Easy to tell apart!

After reading this post you should know all about EF, EF-S, L-grade, black and white lenses to figure out if a lens would fit a certain body or not. Just to sum up, two more examples:

Canon extension tube EF-14. Note the red dot on the lower right: This is the marker that indicates it connects to the camera mount as an EF mount. The other side of this tube has both a red and a white marker, meaning you can mount both EF and EF-S lenses on this end.

Confused yet? The picture above is a 14mm tube. These tubes are used to create space between lens and sensor, which will allow a lens to focus up closer (macro usage). It will however loose infinite focus. As you can see by the dots, you could actually mount an EF-S lens on this tube, then mount the tube on a full frame (“red dot only”) camera. This combo probably would work, but as the EF-S lens only illuminates a cropped sensor area, you may end up seeing a sharp vignette around the image. And of course you’d loose infinite focus due to the tube increasing the distance between lens and sensor.

Another example:

Part of the mount of a Samyang 35mm f/1.4 AS UMC manual lens. Note the red dot: Even though Samyang print the dot inside the mount and not next to it, it is obvious this lens is a “full frame capable” lens (or: compatible with the EF mount). Also note the electronic contacts which I glued on myself to fool the camera of this lens being an automatic lens.