Lens Basics – Extension Rings





In this post, we will be covering an essential lens add-on used in Vision and photography called the extension tube or extension ring. Most commonly used lenses are either fixed focal (having a minimum working distance) or vari-focal. An extension ring is an accessory used in between the connection of a lens to a camera. The purpose of this addition is to primarily move the lens away from the image plane (virtual object plane) in order to increase the focus and magnification.

In other words an extension tube is used primarily for two purposes:

  1. To view a smaller field of object view using a longer focal length, with the working distance remaining constant.
  2. To reduce the working distance between object and lens while using a longer focal length lens.

The disadvantage of extension rings are that they reduce the amount of light reaching the lens, hence necessitating greater exposure setting. This can have a significant impact to image quality and is not recommended where light sensitivity and accuracy is demanding. For further details and enquiries,  do contact us at info@qualitastech.com

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