Getting Started with Camera Lenses

If you’re new to photography or videography, then lens usage and terminology can be confusing. In this guide, we’ll explain common terms, learn how to read a lens, and provide tips to get the best quality.

• Camera Lens Terminology
  • Focal Length
  • Aperture (f-number/f-stop)
  • Depth of Field
  • Image Stabilization
• How to Read a Camera Lens
• Camera Lens Tips & Tricks

Camera Lens Terminology

Lenses are essential components of a camera setup. Understanding key terms such as focal length, aperture, and depth of field will help you achieve the best possible image quality.

Focal Length

The focal length determines how much of a scene the lens captures. It’s the distance, measured in millimeters, from the lens’s center to where the light hits the sensor.

A longer focal length means objects appear larger and the field of view is narrower (less is in frame). A shorter focal length means objects appear smaller and the field of view is wider (more is in frame).

• If you see one measurement stamped on the lens (e.g., 35mm), then it’s a prime lens, meaning the focal length is fixed and cannot change. If you see multiple measurements (e.g., 35mm–100mm), then it’s a zoomlens, meaning the focal length can be adjusted.

Equivalent Focal Length

The equivalent focal length of a lens is the focal length adjusted for the size of the camera’s image sensor.

• For example, a standard full-frame image sensor is 35mm, and the most common standard lens is 50mm (depending on the manufacturer), which is a 1:1 ratio. However, if you mount a 50mm lens to a camera with an APS-C image sensor (which is smaller), then the ratio is 1:1.5 (1:1.6 for Canon), so the 50mm lens has an equivalent focal length of 75mm (80mm for Canon).

Aperture (f-number/f-stop)

Aperture, known as the f-number or f-stop, is measured in increments and indicates how much light passes through the lens. The f-stop is the opposite of the size. This means large apertures have a small f-stop and small apertures have a large f-stop.

The iris is open wider on a larger aperture (e.g., f/2.0), so more light reaches the sensor. A smaller, narrower aperture (e.g., f/16) allows less light because the iris is smaller. It’s just like your eyes.

Larger apertures are recommended for low-light conditions or when a shallower depth of field is required. Smaller apertures are often used for greater depth of field or if you require a bit more sharpness.

Depth of Field

Depth of field describes how much of the foreground and background is in focus relative to the subject. There are three primary factors that determine the depth of field: focal length, aperture, and distance from the subject.

Objects in front of and behind the center are more in focus with a wide depth of field. With shallow depths of field, the central object stays in focus while the foreground and background come out of focus. The quality of this blur is called “bokeh,” which is a desired effect in many different styles of photography and videography.

Canon Quick Tips: Camera Aperture Explained

Image Stabilization

Image stabilization is a technology that helps counteract sudden jitters and other movements to prevent unwanted blur. While there may be slight differences in name and features across manufacturers, the functionality remains the same.

There are several types of image stabilization available, including lens stabilization (OIS), in-body stabilization (IBIS), and digital stabilization (DIS). Both lens and in-body stabilization are mechanical, but digital stabilization uses the camera’s processing to stabilize the image.

• Available image stabilization options vary by manufacturer, so refer to the lens and camera user manuals for more information.

How to Read a Camera Lens

If you’re new to camera lenses, then you’ll see many letters, numbers, and symbols stamped on them. It becomes easier to figure out how to use your lens once you know what these mean.

Let’s look at the Canon RF 24mm–70mm zoom lens as an example. While there may be slight differences and variations among manufacturers, these markings are found on virtually all camera lenses on the market.

• RF: Lens mount system.
  • The lens mounts are proprietary to specific camera manufacturers or models. In this instance, RF is proprietary to Canon. This will vary from lens to lens. Refer to both your camera and lens owner’s manuals for more information.
• 24–70mm: This lens has a variable focal length of 24mm–70mm. Since there are two measurements, it’s a zoom lens.
• F 2.8: The lens has an aperture of 2.8.
  • Sometimes the aperture is marked with “f/” or a ratio. So, the aperture for this lens could also have been equally marked as either f/2.8 or 1:2.8.
• L: Series. Series are manufacturer-specific because not all manufacturers will classify lenses under a specific series.
• IS: Image stabilization.
  • If your lens has image stabilization, then use the switch on the side of the lens to turn it on and off.
• USM: This is the type of autofocus technology this lens uses. It stands for “Ultrasonic Motor,” which is proprietary to Canon.
  • Each manufacturer uses unique autofocus motor technology. Refer to the lens owner’s manual to learn more about its autofocus functionality.
• Ø 82mm: This symbol indicates the mount size for the front lens. You will use this number if you ever need to purchase lens filters, lens caps, or lens hoods.

Other Common Markings

While manufacturers will have additional unique markings, there are a few more common ones that can be found.

• AF/MF: Autofocus and manual focus.
  • If your lens has autofocus, then there’s usually a switch on the side to turn it on and off.
• (xx)ft or m-∞ (infinity): Focus scale. This is used when you’re in manual focus mode.

Camera Lens Tips & Tricks

Once you’re up and running with your new camera lens, here are some tips and tricks to get the best possible results.

• Use a lens hood. It protects your lens from the weather, blocks direct sunlight, and helps prevent scratches or damage if you accidentally drop it.
• Test your lens in multiple environments (indoors and outdoors), at different distances, under different lighting conditions, and with different apertures and shutter speeds to give you an idea of its optimal range.
• Don’t forget to refer to both the lens and camera user manuals; they will provide more information on usage.
• Use image stabilization when shooting handheld. If your camera allows, then turn on IS on both the lens and camera body to help you get clear photos.
  • Turn off image stabilization on both your camera and your lens when using a tripod. Leaving it on can cause micro vibrations.

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