Monday, April 18, 2011

Anatomy of a lens model name

With so many lenses to choose from, here are something crucial to learn about lenses, the model types. I have two lenses, the Canon EF-S 18-55mm F3.5-5.6 IS and the 50mm F1.8 II, such long names for a lens, right? Whether you are a Canon user or a Nikon user, it is very important that you understand why lenses have long model names, what are those numbers about? What's an IS and n F stands for?

Let's use the Canon EF-S 18-55mm F3.5-5.6 IS as our material to dissect on the matter, shall we?

Anatomy of a lens model name:

Lens model (Canon)= <brand> + <generation> + <focal range> + <aperture range> <extra features>

Lens model (all brands)= <brand> + <focal range> + <aperture range> <extra features>

NOTE: any extra set of letters after the aperture range are extra features of a lens, this applies to all lens manufacturers.

Canon has two generations of lenses, the EF and EF-S, the latter being the new generations. Distinguishable marks on both lenses are their red dot and white squares near the back side of the lens. A red dot means a lens is an EF and a little white square means it is from the family of EF-S lenses. EF lenses are the standard lenses made by Canon decades ago when they launched their Single Lens Reflex cameras, or otherwise known as SLRs.  EF-S lenses were only introduced in 2003, therefore, older cameras cannot use EF-S lenses but all cameras can use the EF lenses.

The "S" in EF-S stands for short back focus, the construction of the back end of the lens was designed to sit back deeper into the lens body, this has something to do with the cameras sensor size, which is smaller than the high end full frame cameras. EF-S lenses can only be used by APS-C sensor cameras, in other words, any camera that does not have a full frame sensor can use this lens. To see if your camera body is compatible with the EF-S and/or EF lenses, check the presence of the red dot and white square on the mount ring, it is where the lens is mounted to the camera's body.

Focal Range:
Is the focal length coverage of a lens. 18-55mm means it can cover a focal length of 18mm up to 55mm, obviously. The smaller the number of a lens' reach the wider coverage it can capture in a single frame like an 8mm, 10mm, 16mm, 17mm, 18mm, etc.  The higher the number of a lens' focal reach, the longer or farther it can see, 85mm, 100mm, 135mm, 200mm, etc. Meaning, if you are using an 18-250mm, you can zoom up to 250mm, that's pretty far.

Aperture Range:
Defines how much light the lens can take in. It also defines how much the blades inside the lens can open up, to allow light in. The smaller the number, the wider the aperture can open. The wider the aperture can open, the more light it can take in; the faster the shutter will be. You will want a faster shutter speed during low light conditions wherein it will be challenging (but not hard) to keep your subjects in focus because the shutter is slow. The shutter is low because the it needs more light to capture the subject (clearly), so it remains open for a couple of milliseconds or even seconds in a single take. So if you have a lens with a wider aperture, the faster the shutter speed will be.

Canon EF-S 18-55mm F3.5-5.6 IS  - The widest the aperture is at F3.5, as the user zooms in a subject, the aperture changes down to F5.6 maximum.

Canon EF 70-200mm F2.8 L IS USM - The aperture can be wide open at F2.8 in the entire focal range.

Also, maximum aperture opening can also affect how much depth of field can be achieved by your lens.   A depth of field is the distance between the farthest and nearest objects to the sharpest point in a frame. In other words, this is the blur of the foreground and the background of a subject. The wider the aperture, the shorter the depth of field is, and the blur is creamier.

So, aperture affects two aspects,  1 is the shutter speed and 2 is the depth of field.

Extra Features:

Canon EF 70-200mm F2.8 L IS USM - This lens has IS and USM

IS - stands for Image Stabilizer. Most lenses that have apertures smaller than F2.8 have IS to compensate for the slow shutter speed the camera will be experiencing during low light shooting. Slower shutter speeds means that during low light, the photographs' clarity will be affected due to camera shake (user related issue), Image Stabilization corrects this.

USM - Ultra Sonic Motor, lenses with USM focuses silently and faster. My 50mm lens does not have USM, and it does focuses with a bit of noise and it takes a while (milliseconds) for it to get a focus point in low light conditions.

L - Stands for luxury. If see a Canon lens that has a letter "L" in the name, it is surely to be very expensive.

Other examples of lens names from third party lens manufacturers:

Tokina 11-16mm f/2.8 AT-X

Sigma 24-70mm f/2.8 IF EX DG HSM

Tamron 70-200mm f/2.8 Di LD (IF) Macro


  1. Ei!!! Your posts on photog are informative. Sana nga lang Nikon ka para mas nakakrelate ako. Hehe. I'm new to DSLR's so I take in all the info I've read about

  2. ang hirap naman nito. pag meron na lang ako saka ko pagaaralalan.