Jumbo 300mm Canon extension tube with autofocus

thingiverse

This massive 300mm extension tube for Canon cameras is a bit overkill, but it lets you achieve ultra-macro magnifications beyond 1x using long lenses! (100mm+) It reuses the metal mount pieces from Kenko extension tubes to make attaching it to your lens and camera smooth, but replaces the original lens contact system with its own. This keeps the electronic aperture and autofocus control of your lens intact. The advantage of using a long extension tube with a long lens is the exceptionally high working distance it allows, as shown in the performance notes below. The assembled weight is 340 grams. If you're looking for something less extreme, a 150mm version of the tube is also available. **300mm tube 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 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 Lens notes: - Huge focus dial throw gives a large, practical range of magnifications - Lens collar is very helpful for mounting light accessories and using 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 Lens 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 it 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. **The current version of the tube is v2.** The documentation for the previous version (v1) can be found here. If you liked this tube, please also check out my twin-flash arm system for the MT-24EX that's shown in the second photo, and my diffusers for the MT-24EX.