Tech Talk – Aquatech BT-145 and the Canon 24-70mm f/2.8L II

Aquatech's "Scout" 5D Mark 3 Sound blimp with BT-145 Tube

Aquatech’s “Scout” 5D Mark 3 Sound blimp with BT-145 Tube

The Canon EF 24-70mm f/2.8L has been a very topical issue for blimp makers and users alike. The second version (and current) 24-70mm f/2.8L was released in 2012 and is a massive step up in optical performance for this workhorse of a lens. Because of the fact that this new version is physically longer when set to longer focal lengths than when set to wider focal lengths any blimp tube has to vary in length accordingly to avoid massive vignetting.

Aquatech’s BT-145 lens tube is designed to solve the problem created by the new 24-70mm lens design. There have been a few users struggling a little with how to set it up so that the BT-415 tube will reliably zoom in and out. I consulted with Aquatech who gave me the following advice:

  1. Ensure that the rubber zoom ring is pushed as far forward on the lens zoom ring as possible without going past it.
  2. Screw the back part of the BT-145 onto the blimp
  3. Gently push the front element of the tube into place and twist so as to push the front element of the 24-70mm lens as deep into the foam as possible
  4. Apply gentle pressure to the back of the camera (with the blimp back open) as you push and twist

You can also watch this video I put together to see the best way I’ve come up with to make the BT-145 work with my 24-70mm Version 2.

AT24-70 from Angus Young on Vimeo.


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