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Close-up: Adding Extension

Every lens focuses by moving its elements closer or further away from the film or imaging sensor. One of the most fundamental means of getting into the realm of macro is to add even more range of movement for the lens elements. If you move the lens elements closer to the film plane, you will be focused on objects further away. If you move things further away form the film plane you will be focused on closer objects. Moving the lens elements further away is known as adding extension to the lens.

Here are a few of the most common ways of achieving greater extension:

Macro Lenses

A macro lens is merely a regular lens with a greater than normal extension capability built-in.  They tend to have high-quality elements to maximize their ability to record a flat field of view. By convention, macro lenses tend to come in short, medium and long focal length ranges. We'll look at this in more detail in another few weeks. Many macro lenses have enough built-in extension to reach 1:1 life size all on their own which makes them quite convenient. Macro lenses can also serve double duty for shooting regular subjects with the same focal length.

Advantages

  • Excellent quality
  • Convenient
  • Can be used as regular lenses as well

Disadvantages

  • Not cheap
Macro lenses

Extension Tubes

An extension tube is merely a hollow ring that can be mounted between a lens and camera to provide greater extension. While extension tubes can be used in conjunction with macro lenses, they can also be used with normal lenses to provide greater magnification. If you use a tube on a zoom lens though, you will probably need to refocus if you zoom since the extra extension is not part of the lens's normal design. Not all extension tubes pass the electrical signals necessary for modern cameras to focus and meter, so keep this in mind if you are in the market for tubes.

Advantages

  • Relatively inexpensive
  • Relatively compact and easy to carry
  • No added glass layers

Disadvantages

  • Not all tubes retain metering or aperture
  • Must refocus if you zoom
  • Difficult to get the length you want
Extension tubes

Bellows

While extension tubes generally come in fixed lengths, bellows by there very nature provide variable amounts of additional extension. These are not for everyone though as they tend to be big, bulky, and a bit cumbersome to use. Due to their construction, most do not mate electronically with the attached lens, limiting functionality on many camera bodies. Without this electrical contact for instance, many Nikon bodies will not even meter let alone focus. Still, a good bellows can be a joy to use as it provides the ability to get variable extension, and thus variable reproduction ratios. Many people want a bellows but there are better options for most needs.

Advantages

  • Great flexibility — variable length extension
  • Easy way to get a lot of extension

Disadvantages

  • Expensive
  • Bulky
  • Cumbersome to use
  • Does not couple metering or aperture
Bellows

After going through some more equipment options next week, we'll start looking specifically what to do with all these toys.


Date posted: June 6, 2004

 

Copyright © 2004 Bob Johnson, Earthbound Light - all rights reserved.
Permanent link for this article
 

Previous tip: Close-up: Building on a Solid Foundation Return to archives menu Next tip: Close-up: Stacking, Reversing and Other Lens Gymnastics

Related articles:
Close-up: Welcome to the World of Macro
Close-up: Larger Than Life
Close-up: Building on a Solid Foundation
Close-up: Stacking, Reversing and Other Lens Gymnastics
Close-up: Choices, Choices and More Choices
Close-up: Angle of View, Working Distance & Background Control
Close-up: Depth of Field and the Film Plane
Close-up: Focusing Rails
Close-up: Lighting for Macro
Close-up: Macro Flash Brackets
Close-up: Working in the Field
Close-up: Macro on the Cheap
Close-up: Chasing (and Hopefully Photographing) Butterflies
Close-up: Resources for Further Information
 

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