Beginner’s Guide to Understand Lens Structure


A camera lens is a distinguished combination of various glasses including Concave, Convex, Concavo-Convex etc. which helps to bring in the focus of image better and helps you to adjust the focus accordingly. “Aperture” enables you to function the clarity of the content and control the device.

Lens specification: It is a vital part of using the camera and functioning depends upon this factor. Here are some quick specifications mentioned for your reference:

Focal Length Range: It can either be fixed or variable which is often mentioned on the camera in “mm”. For eg: 50mm or 100-400mm. Fixed Focal Length is the one that does not change and remains constant while clicking. There is no separate zoom option available to take the image. In Variable Focal Length, maximum and minimum focal lengths are mentioned i.e you can take a picture in-between 100-400mm.


Aperture supported: This lies inside the device and comes in two variants: Fixed Aperture and Variable Aperture. For instance: a lens with focal length range of 100mm – 400mm, F4.5 – F6.3 (as mentioned on the lens) implies, the minimum F-number at 100mm is F4.5 while at 400mm, it is F6.3. The F-number range also changes when clicking an image between 100mm to 400mm focal length and would lie between F4.5 to F6.3. There are zoom lenses which have fixed aperture rating, such as 24-105mm, F4.0.

Manual/Auto Focus: The camera has these two essential functions and can be toggled between these two options while taking images. In Manual Focus, the ring has to be adjusted by hand or manually, this is particularly desirable when the auto focus is not accurate. In Auto Focus, the focus is already adjusted inside the camera and lens will automatically focus on the focus points.

Image Stabilization: This is an internal system of lens movement, which helps to avoid the hand shake error to some extent. Some lenses even give the advantage of 3 F-stops through image stabilizer. Different lens manufacturers have allotted distinguished terms for image stabilizer. Here are some of them:

  • Canon – IS – Image Stabilization
  • Nikkor/Zuiko – VR – Vibration reduction
  • Sigma – OS – Optical Stability
  • Tamron – VC – Vibration Correction

Quality of lens: Different brands also have various specifications to highlight that the lens is of higher quality. Higher quality means, the glass elements of the lenses reduces the lens imperfections, the lens is weather proof and the cost becomes higher. For e.g. Canon mentions “L” with a red ring or white construction to signify that the lens is of high quality. Similarly Nikkon lenses have “ED” mentioned to signify “Extra low Dispersion” glass mentioned inside the lens.

Filter Mount: Every lens needs filter of a specific size and this can be found on the information written at the boundary surface of the font glass. Different industrial filter sizes are 52mm, 58mm, 62mm, 77mm, 95mm, etc and mostly lenses have either of these.

Focusing Motor: Canon lenses especially highlights whether the lens has a dedicated focusing motor for instant accurate focusing. This is denoted by “USM” which stands for “Ultra Sonic Motor”.

Minimum Focusing Distance: It is generally mentioned on the lens surface in terms of feet and meters (for e.g., 0 .45m/1.5 ft) which denotes that the image in focus should be at least this much (distance mentioned) distant to allow lens to focus. Sometimes people go too close and then wonder why lens is not focusing and blame it on the lens. However, it is not a defect. You must be at least at minimum focusing distance.


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