Friday, 8 November 2013

Stacking Lenses with Coupling Rings for Extreme Macro Photography

To get started with using coupling rings for extreme macro photography; let us fist discuss the principle behind, so as to understand what’s really going on when we stack lenses together.

What is a Coupling Ring?

Coupling Ring For Macro Photography
Coupling Ring For Macro Photography

Coupling rings are adapter which has male filter threads on either side. They allow you to connect two lenses (of the same filter size) by their filter mounts (face to face).

How does a Coupling Ring Achieve High Magnifications

Lenses are designed to shrink subjects so as to fit a 24x36mm sensor. When you take a picture of the Burj Al Arab you are actually shrinking it to fit the size of your sensor. Now if you flip the lens around it will do the opposite it will make tiny things appear huge. The principle behind working of a coupling ring is to use a reversed lens in front of a lens mounted normally so that the reversed lens will first magnify the scene / subject in front of it and then the lens which is mounted normally on the camera will capture an image of the enlarged subject; brilliant isn't it?

Coupling Ring For Macro Photography
Photo by: Paul

Tips for using Coupling Rings for Extreme Macro Photography

coupling ring macro photography
Photo by: Dr Kalesh Sadasivan

  1. For lens stacking you need at least two lenses the primary lens (the one mounted directly on the camera) will be mounted normally.
  2. It helps if the primary lens is of the same brand as the camera as this will make sure the aperture works as normal.
  3. The primary lens should be a long focal length lens (longest you have for maximum magnification).
  4. The secondary lens is mounted in reverse (screw on to the filter thread of the primary lens) using the coupling ring.
  5. Smaller the focal length of the secondary lens is; higher the magnification.
  6. Secondary lens is always used at its maximum aperture (wide open / smallest f number).
  7. It doesn't matter which brand the secondary lens is as it is mounted using its filter thread. You can even reverse enlarging lenses.

  8. macro photography lens stacking technique using coupling rings
    Photo by: Dr Kalesh Sadasivan

  9. With lens stacking using coupling ring the magnification achieved is the ratio of the focal lengths of the two lenses. A 50mm lens (secondary) reversed on a 100mm lens (primary) would give you 2.0x magnification. And a 50mm on 200mm would give 4.0x magnification.
  10. Remove any filters on the lenses before stacking them using a coupling ring. The closer the lenses are the better the image quality. Filters are additional glass elements and they will deteriorate image quality.
  11. It is better to use wide angle prime lens as the secondary lens. It is not recommended to use Long and/or heavy lenses reversed as they would place too much strain on the filter mount.
  12. If the secondary lens has floating elements (macro and fast wide angle lenses) try some test shots with the lens set for close focus and also with focus set for infinity. One of those settings will always give better image quality than the other.
  13. When some lenses are stacked together you will either get a circular image or images which are cut off at the corners. This is caused by the diaphragm of the reversed lens. The problem is most severe when you are using a short focal length lens as your primary lens and your secondary lens (reversed lens) has a small maximum aperture (slow lens). To avoid this effect set the focus of the primary lens to its closest focusing distance if this does not resolve the issue try using an extension tube.
  14. Remember when lenses are stacked the contact points and the reverse element of the secondary lens is exposed. Working distances are often in millimeters and focusing is done by moving the camera forward and backwards. So if you are not careful chances are you will bump your lens on the subject or the surface in which it is when trying to focus. Add a short extension tube on the secondary lens to act as a lens hood or use retro step rings which makes it possible to attach filters / lens hoods / ring or twin flash etc to the rear of the lens.
  15. Even if the two lenses you need to stack does not have the same filter size you can use step up or step down rings to fix them on the coupling ring.

Coupled lens Magnification and Working Distance for Full Frame Camera

Main lens   Reversed lens Working distance Subject size Magnification
200 mm      50 mm                40 mm           9 × 6 mm        4:1
200 mm       24 mm        40 mm          4.5 × 3 mm        8:1

Advantages of using Coupling Rings for Macro Photography

  1. Low Cost
  2. Small, light weight, easily portable
  3. Reversed lens can be of any make

Disadvantages of using Coupling Rings for Macro Photography

  1. Rear element and coupling mechanism exposed
  2. Some lens combinations produce circular image

Related Reading

  1. Turn Your Kit Lens into an Extreme Macro Lens with Full Aperture Control
  2. How to Make Aperture Work as Normal With Lens Reverse Technique
  3. How to Lock a Lens at a Certain Aperture
  4. Reverse Lens Macro Photography Using Lens Reverse Ring
  5. How to turn any Lens into a Macro Lens the Lens Reversal Technique