Aperture blades
Internal blades inside the lens that open and close to control how much light enters. They physically form the aperture shape, which affects how background blur (bokeh) looks.

Aperture ring

A ring on some lenses that lets you manually change the aperture (f-stop) directly on the lens instead of using the camera. It provides physical, on-lens control of exposure and depth of field.

Aspherical / ED / FL elements

Specialized glass elements inside the lens designed to reduce distortion, color fringing, and improve sharpness. These improve image quality optically and are not something you adjust while shooting.

Auto/manual focus switch

A switch that changes the lens between autofocus and manual focus. Autofocus lets the camera focus for you, while manual focus means you turn the focus ring yourself.

Distance scale

A marking on some lenses that shows how far away the lens is focused, such as feet or meters. It displays focus distance and is especially useful for manual focus work.

Filter thread

The front ring of the lens where you attach filters, such as UV, ND, or polarizers, measured in millimeters like 67mm. It determines compatibility with filters and accessories.

Focal length

How “zoomed in” or “wide” the lens sees. It’s measured in millimeters, like 24mm, 50mm, or 200mm. Lower numbers show more of the scene, while higher numbers make distant subjects look closer and more compressed.

Focal length selected

The specific focal length the lens is currently set to at that moment. On a zoom lens, this changes as you turn the zoom ring. On a prime lens, it stays fixed because the lens has only one focal length.

Focus breathing

A slight change in framing that happens when adjusting focus, most noticeable in video work. It is a side effect of focusing rather than an intentional setting.

Focus limiter switch

A switch that limits the range of distances the lens will focus on, such as excluding very close focus. This helps speed up autofocus by reducing how far the lens has to search.

Focus ring

The ring you turn by hand to adjust focus manually. It lets you choose exactly what part of the image appears sharp.

Image stabilizer

A feature that helps reduce blur from small hand movements while shooting. Different brands call it different things, but it all refers to stabilization built into the lens.

Internal focus

A design where focusing happens inside the lens without the front element moving. This keeps the lens size and balance consistent while focusing.

Internal zoom / external zoom

Describes whether the lens physically changes length when zooming. Internal zoom lenses stay the same size, while external zoom lenses extend outward.

Lens hood mount

The area where a lens hood attaches to block stray light and reduce glare. This helps prevent unwanted light from affecting the image.

Lens mount

The part of the lens that connects it to the camera body, such as Canon RF, Sony E, or Nikon Z. It determines which cameras the lens can be used with.

Macro ratio / magnification ratio

Indicates how large a subject appears on the camera sensor, such as 1:1 for true macro. It measures close-up capability rather than zoom distance.

Manual focus override (full-time manual focus)

Allows you to adjust focus manually even while autofocus is enabled. This combines autofocus speed with manual precision.

Maximum aperture

The widest the lens can open to let in light, written like f/1.8, f/2.8, or f/4. A wider maximum aperture lets in more light and can create more background blur. Smaller f-numbers mean a wider opening.

Minimum focusing distance

The closest distance the lens can focus on a subject. It determines how close you can get while still achieving focus.

Weather sealing

Protective seals built into the lens to guard against dust and moisture. This improves durability and reliability in harsher environments.

Zoom ring

The ring you turn to change the focal length on a zoom lens, such as moving from 24mm to 70mm. This physically changes how wide or tight the frame appears.