If you’re using a USB 2.0 equipped camera like the Canon 5D Mark III or Sonly A7 series, then the TetherBoost won’t be necessary at all. USB 2.0 cables carry a maximum of 500mA of current which is easily provided by even the weaker USB ports on a MacBook Pro or iMac. Modern cameras like the Nikon D810, Canon 5D Mark IV, and Phase One IQ series that use USB 3.0 for tethering present a new issue. Unlike USB 2.0, USB 3.0 devices can draw a maximum of 900mA of current. This is no problem for the more robust ports on a Mac Pro or PC workstation, but the USB ports on MacBook Pros and iMacs do not offer the same performance. While they can generally supply enough current to sustain a connection with a standard 15-foot tether cable, the same cannot be said for longer cable runs. That’s where the TetherBoost comes in. For DSLR cameras that use the USB 3.0 Micro-B Connection like the Canon 5D Mark IV, 5DS and Nikon D810, my experience has shown that a TetherBoost setup is required in order to use cables longer than 15 feet when tethering with a MacBook Pro. I always set it up at the beginning of the day rather than stopping to reconfigure the cable path after the first or second dropped connection. I like to use the TetherBoost when tethering to my Mac Pro as well, just to be safe. Though an external power source is not required in order to take advantage of the benefits of the TetherBoost, I have found it to add quite a bit of stability when used in conjunction with cameras that utilize a USB 3.0 Micro-B connection.