This massive 3D-printed 300mm extension tube for Canon cameras is a little bit over the top, but allows you to achieve ultra-macro magnifications beyond 1x using long lenses! (100mm+)

If you'd like to build this tube yourself, please check out its Thingiverse page here.

It reuses the metal mount pieces from Kenko extension tubes to make mating it with your lens and camera smooth, but replaces the original lens contact system with its own. This preserves the electronic aperture and autofocus control of your lens.

The advantage of using a long extension tube with a long lens (rather than adding a close-up lens) is the exceptionally high working distance it allows, see the performance notes below.

Performance with the Sigma 180mm f/3.5 APO Macro DG HSM

• Minimum magnification 1.7x at 240mm working distance
• Maximum magnification 5x at 170mm working distance (That means that a subject 7.2mm x 4.8mm completely fills the frame!)

Compare these numbers to the bare Canon MP-E 65mm, which offers a similar magnification range:

• Minimum magnification 1x at 100mm working distance
• Maximum magnification 5x at 41mm working distance

Sigma 180mm notes

• Huge focus dial throw gives a large, practical range of magnifications
• Lens collar is very helpful for mounting light accessories and to use as a handle

Performance with the Canon EF-S 55-250mm IS

• Focal length 70mm: Dust on the front element is in sharp focus!
• Focal length 100mm: 5.6x -> 6.3x magnification at 16mm -> 27mm working distance
• Focal length 120mm: 2.5x -> 2.6x magnification at 46mm -> 51mm working distance
• Focal length 135mm: 2.2x -> 2.3x magnification at 88mm -> 92mm working distance
• Focal length 200mm: 1.5x -> 1.9x magnification at 267mm -> 315mm working distance
• Focal length 250mm: 1.1x -> 1.2x magnification at 370mm -> 415mm working distance

Canon 55-250mm notes

• Image stabilisation is surprisingly helpful for steadying the shot for framing.
• Setting the focus ring at infinity actually increases both the working distance and the magnification (because the end of the lens collapses towards the body).
• Focal lengths in the 100-150mm range are the most useful.
• At 250mm the subject is so far away that framing and lighting the subject is difficult. Maybe good for natural light photos in bright conditions?
• End of the lens rotates during focusing, but not during zooming Zoom position is not held very strongly - so bumping the end of the lens is really annoying
• This is definitely not an Apochromatic lens - strong longitudinal chromatic aberration present, with magenta fringes on out-of-focus areas in front of the focal plane, and cyan fringes beyond.