2010-10-09

DIY Macro Photography II: Reversed Lenses

Ingredients

  • Canon FD manual lenses (28mm f2.8 and 50mm f1.8).
  • 77mm-77mm reversing ring.
  • 77mm-55mm and 77mm-52mm step-up rings.
  • Canon FD rear lens cap.

Construction

Most of this approach is very simple to put together. All you need to do is reverse mount one of the manual lenses onto the front filter thread of one of your digital camera lenses. This is done using two adapters in my case. I have some L-series Canon lenses, so chose a 77mm reversing ring for maximum flexibility. In order to use this ring on the manual lenses, a step-up adapter is needed (55mm thread for the 50mm lens, 52mm thread for the 28mm lens).

The one stumbling block I found was stopping down the FD lenses. The FD design has a number of catches and levers on the rear face of the lens. Unless particular pins are pressed in, the lens will not stop down. You can work around this by poking the pins and levers with a screwdriver, then gluing them in place.

Instead of fiddling around with a screwdriver I decided to modify an FD rear lens cap to fool the lens into thinking it was mounted on a camera body. This hack is easy to do:

  • First, cut the central section of the lens cap away. I cut the cap right back to the edge so that there would not be any bits poking into the image frame.

    • Next remove the stop tab on the edge of the cap. Normally this prevents the lens cap from rotating all the way round. This normally allows the lens to distinguish between and lens cap and a camera body. By removing the tab we can rotate the cap all the way around and fool the lens.

    • Mount the cap and depress the stop-down lever on the lens. The lens is now stopped down, the lens cap also doubles as a handy lens hood.



    Once this is done, simply use the appropriate reversing and step-up rings to mount the manual lens onto the front of one of your digital lenses. The picture below shows my complete setup with the 50mm lens mounted onto my 100-400L.


    Use

    I found the following method worked best for me:
    • Set both lenses to manual focus, set focus to infinity.
    • Leave the manual lens aperture wide open (f1.8 on the 50mm lens).
    • Frame the image and set focus using focus rails.
    • Set the main lens to stop all the way down (f40 on the 400mm lens).
    • Take the image.

    Results and conclusions

    As expected, the 28mm lens gives greatest magnification, but results in a large amount of vignetting. Combining the 28mm lens with the 400mm lens gives about 7-8x magnification. I found that the 50mm lens combined with 300mm on the main lens gives the most useful magnification (somewhere around 5x).

    Image quality is reasonably good. The main issues are a lot of cyan/red chromatic aberration which can be partially corrected during raw processing. The other difficulty is the extreme limited depth of field, however this is just an aspect of macro photography

    Some example images below:










    2 comments:

    1. Hello James,

      looking over the web to find a solution to a great vignette problem I've found your blog. I'm experimenting a reverse 28-70 2.6 Tokina (77mm diameter) over a 80-800 2.8 Tokina (77mm diameter), but I cannot step over f/5.6 'cause there begins to create a huge vignette. At f/32 the frame a small circle! It can be caused bye the front lens diameter? This vignette could be due to the diameter difference between the frontal and back lenses?
      Thank you,
      Fabio

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    2. Hi Fabio,

      I've found it's a matter of experimentation. As you say, I'm sure the relative diameters of the lenses is a factor. In general I leave the reversed lens as wide open as possible and stop down the primary lens. Even then I still have to do a drastic crop to remove the vignette. I guess that's what you get for doing things on the cheap!

      James.

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