Understanding Canon Lenses

When you are new to photography and are looking for information about lenses, you might come across descriptions for lenses like this one:

Canon EF 500mm f/4L IS USM

This is the official name of my 500mm telephoto lens. The name contains a lot of terms that may sound strange at first. So lets break it down into small pieces and explain everything in detail (including some terms that do not occur in the description of the lens above):

Canon: Well, that’s pretty obvious. It’s the manufacturers name.

EF: EF means “electro-focus” and means that this is an autofocus lens. With a few exceptions (see below), all Canon lenses for EOS cameras contain the “EF” term.

500mm: The focal length.

f4: The largest possible f-stop.

L: L means “luxury”. This is Canon’s way of saying that this is a professional and especially good lens. L lenses contain the best glass, are normally weather proof and are built much more robust than other lenses. That does not mean that non L lenses are always bad. For example, the Canon EF 100mm f/2.8 Macro USM is not a L lens but is still a very good and very sharp lens. I use that lens very often.

IS: IS indicates image stabilization. Many of the new Canon lenses introduced during the last 10 years feature this technology. With IS you can hand hold a lens at longer shutter speeds and still get sharp pictures than without it. IS also works well on a tripod with most IS lenses.

USM: USM means “ultrasonic motor” and indicates a very fast and silent autofocus motor. Canon has integrated USM technology in most of it’s L lenses and also many others.

Macro: This indicates that the lens is a special macro lens, especially designed for working at close distances, often reaching a magnification ratio up to 1:1. This lenses also work as a normal lens and focus to infinity (except the Canon MP-E 65mm f/2.8 1-5x Macro Photo which only works for magnification ratios between 1:1 and 5:1).

EF-S: These are lenses designed only for EOS cameras with an APS-sized sensor like the EOS 40D or EOS 450D. They are not intended to work with full frame cameras like the EOS 1Ds Mark III.

MP-E: This is used only for one lens, the already mentioned Canon MP-E 65mm f/2.8 1-5x Macro Photo which is a special macro lens designed for extreme close-up work between a magnification ratio of 1:1 and 5:1. If you want to shoot portraits of insects, this is your lens. Nikon and other companies currently don’t offer something similar. It’s not an L lens but the image quality is of the highest standard nonetheless.

TS-E: Those lenses are called tilt-and-shift lenses. They are very popular among architecture photographers. Some photographers also use it for landscape work. They don’t have EF in there name as they don’t support autofocus.

DO: DO means “diffractive optics”. Those lenses are smaller and more compact than non DO lenses. Currently Canon offers only two DO lenses, including the EF 400mm f/4 DO IS USM. This lens is very small for a f4/400mm lens but also quite expensive. Currently it does not seem like Canon will introduce many more DO lenses, but in the future this may change. It would be great to hava a 4/500 or 4/600 with 30% less weight than the current models.

Zoom lenses are often described like this:

Canon EF 70-200mm f/4L IS USM

This means that it’s an 70-200mm lens with a fixed maximum aperture of f4 over the whole focal length range.

Canon EF 100-400mm f/4.5-5.6L IS USM

This means that the lens has a variable maximum aperture from f4.5 at 100mm to f5.6 at 400mm.

Now you should have an idea how to read a Canon lens description. The terms are not always written in the same order. So you may also find “EF 4/500L IS” or something similar.