An External Autofocus for DSLRs

Most modern DSLR cameras support shooting full HD video, which makes them a great cheap option for video production. However, if you’ve ever used a DSLR for video, you’ve probably ran into some limitations, including sluggish autofocus.

Sensopoda tackles this issue by adding an external autofocus to your DSLR. With the camera in manual focus mode, the device drives the focus ring on the lens. This allows for custom focus control code to be implemented on an external controller.

To focus on an object, the distance needs to be known. Sensopoda uses the HRLV-MaxSonar-EZ ultrasonic sensor for this task. An Arduino runs a control loop that implements a Kalman filter to smooth out the input. This is then used to control a stepper motor which is attached to the focus ring.

The design is interesting because it is rather universal; it can be adapted to run on pretty much any DSLR. The full writeup (PDF) gives all the details on the build.

7 thoughts on “An External Autofocus for DSLRs

      1. hej,

        first of all: thank you :)

        second: sam is correct! since we can mount the system on any tripod/monopod/fig rig/slider/you-name-it, the electronics are in front of the camera – for now!

        we would have loved to shrink down everything into a small box or similar, but due to time constraints we simply couldn’t. so we went the other way to show everything in a nice and open way.

        cheers!

  1. hej,

    first of all: thank you :)

    second: sam is correct! since we can mount the system on any tripod/monopod/fig rig/slider/you-name-it, the electronics are in front of the camera – for now!

    we would have loved to shrink down everything into a small box or similar, but due to time constraints we simply couldn’t. so we went the other way to show everything in a nice and open way.

    cheers!

  2. I use an MTO 1000AM f/10.5 Manual focus lens quite often with a 2x teleconverter & thought this seemed just the thing when I searched Google for adding auto focus, I have some questions.

    What sort of range can you get with that ultrasonic sensor?

    I quite often photograph the moon would the vacuum of space present a problem?

    The MTO is quite a big lens does the laser cut wooden gear come in different sizes and what sort of torque can it take?

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