First time fancy camera owner? The names and specs of lenses can be confusing, so let us teach you how to make sense of all those numbers.
One of the very first questions asked by newcomers to the DSLR world is, “What lens should I get?”. By learning how to read the names and barrel markings of lenses, you’ll teach yourself about all the available options and be able to make a better decision.
The Lens Naming Pattern
Camera lenses follow a systematic naming convention that states the optic’s capabilities. The name of a camera lens is best remembered as being a formula. If you understand this formula, you can tell the difference between lenses by simply reading their names.
[brand] [focal length(s)] [maximum aperture] [other designations]
|Brand||Focal Length||Max Aperture||Other|
The brand tells you who makes the lens. It will be a manufacturer’s name, such as “Nikon”, “Canon”, or “Sigma”. This portion may also designate what sort of cameras the lens is compatible with. For example, “Canon EF” lenses work with all Canon EOS cameras, while “Canon EF-S” and “Sigma DC” lenses only work with cameras that contain APS-C sized sensors.
The focal length describes the lens’ field of view. If it’s a zoom lens, the focal length will read something like “18-200mm”. This means the lens is capable of utilizing all of the focal lengths from 18mm (wide) through 200mm (telephoto). If it’s a prime lens, it will only have one focal length, e.g. 50mm.
Aperture is the hole in the lens through which light passes. The maximum aperture describes the widest diameter to which this hole is capable of adjusting itself. A maximum aperture might be f/1.8, f/2.8, f/4, etc… Lower numbers let in more light, making faster shutter speeds possible.
A lens name with a range of max apertures indicates that the diameter size changes with the focal length. For example, “18-55 f/3.5-5.6” means:
- At 18mm, the maximum aperture is f/3.5.
- At 55mm, the maximum aperture is f/5.6.
- At focal lengths in between, the max aperture will be a value between 3.5 & 5.6.
Finally, other designations describe various other features of the lens. For example, a lens that can focus on extremely close subjects and make them appear life-size will say “macro”. Lenses featuring mechanisms that compensate for camera shake to reduce blur will have a designation that says so — Canon calls this IS (Image Stabilizer), Nikon calls it VR (Vibration Reduction), and Sigma denotes it as OS (Optical Stabilizer).
Canon EF 70-300 f/4-5.6 IS USM
This is a Canon lens for their EOS line of autofocus cameras. It has a focal length range from 70mm (moderately telephoto) to 300mm (telephoto). The maximum aperture at 70mm is f/4 and the maximum aperture at 300mm is f/5.6. It has an Image Stabilizer, and a USM motor for efficient automatic focusing.
Sigma 17-70mm f/2.8-4.5 DC Macro for Canon autofocus
This is a Sigma lens whose focal length ranges from 17mm to 70mm. The maximum aperture at 17mm is f/2.8, and the maximum aperture at 70mm is f/4.5. DC means it’s designed for digital cameras with APS-C sized sensors. It’s a macro lens capable of focusing on very close subjects, and it’s compatible with Canon EOS (autofocus) cameras.
Canon EF 50mm f/1.4 USM
This is a Canon 50mm prime lens for their EOS line of autofocus cameras. The maximum aperture is f/1.4, and it has a USM motor for efficient automatic focusing.
Alright, here’s a lens barrel with quite a few markings. They are:
- Focus Window - Shows the current focus distance. Subjects which are this far from your lens will be sharply in focus. On the lens shown, the top line (green) shows measurements in feet, and the bottom (white) shows them in meters.
- Focal Lengths - This is a zoom lens, and this marking shows its range of focal lengths. In this case, 24mm to 105mm.
- Zoom Ring - The focal length changes as you turn this zoom ring, and the vertical line indicates the current setting.
The macro marking indicates this lens is capable of focusing at a close distance. “0.45m/1.5ft” is the closest distance at which your subject will be sharp and in-focus. Any closer and it will blur.
Here you can see the lens name printed at the top of the barrel near the glass. The name includes all the most important specifications - manufacturer, focal length range, maximum aperture, and other designations such as “image stabilizer”.
Around the edge of the glass is the filter size (77mm for this lens). This is the number you need to know when purchasing accessories like filters and lens caps. Also, the focal length range (24-105mm) and maximum aperture (1:4 for f/4) are repeated.
Know the Convention, Know the Lenses
The fact is you don’t need to memorize every lens out there. When you understand the different components that go into making and naming a lens, you get a very good feel for the range of optics on the market. By reading and understanding the name of an unfamiliar lens, you’ll instantly get a feel for its basic capabilities… and all you have to do is check out the markings.