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Tech question: Possible with follow focus using internal motors?
  • Hey,

    If someone was given full access to the protocols of the lens control, would it be possible to make a usable follow focus using the internal motors of the lenses? We know these motors can move fast when autofocusing. I know about the Okii and other controllers for Canon that use the usb, but that moves in quite coarse steps, and is not really usable for precise pulls. I realize that it is a longshot to see this functionality in dslrs, but for the dedicated videocameras like c300/af100 a nice always calibrated internal follow focus would be really nice!

    Are there any technical reasons why this wouldn't be possible?

  • 8 Replies sorted by
  • man hours in developing it i say. the principles are there with the on screen touch focus. what i would like is to have a preset A and B position with timer then hit record and it will pull focus based on those inputs.

  • If someone was given full access to the protocols of the lens control, would it be possible to make a usable follow focus using the internal motors of the lenses? We know these motors can move fast when autofocusing.

    Yes, it is possible. Just hard to do.

    With Wi-Fi cameras it can be simpler.

  • Birger Engineering has such a product already. http://www.birger.com

  • @bmorgan83 Cool, I remember that unit. This video is two years old, was this adapter ever released? Is it for sale anywhere?

  • Does anybody know the protocol for 4/3 lenses (not m4/3, if there is any difference)?

    Tapping the contacts from the 4/3-m4/3 adapter would be easy and controlling the high end Olympus lenses with some external device would be really cool.

  • @Psyco Agreed! But it would have to be more precise than the infinitely spinning focus rings on the barrels. Working with proper mechanical 2/3" lenses every day, it is just frustrating to focus with the laggy and unprescise fly-by-wire m43 lenses. I think fly-by-wire could be more precise with proper hard stops...

  • @AndersM

    would it be possible to make a usable follow focus using the internal motors of the lenses?

    With Wi-Fi cameras it can be simpler.

    @Vitaliy_Kiselev is right, it's already almost possible using Wifi control with the GH3 (and it should be the same for the GF6 and G6), and doing some dev/scripting using what is described in this topic : http://www.personal-view.com/talks/discussion/6703/control-your-gh3-from-a-web-browser-now-with-video-/p1) :

    The good things :

    • with the wifi focus control, you have 4 commands : wide fast / wide slow / tele fast / tele slow
    • with the wifi focus control, you have 256 values from minimum to infinity
    • each time you call one of these functions, the GH3 returns the value of the actual focus state (from 0 to 255)
    • you could use the "touch to focus" or the manual focus functions to memorize the focus points you're interested in, and then use them in your script

    The complexity :

    • the speed depends on the lens used. So you basically have to handle every lens model when you code the focus application
    • the network / processing delay when executing a focus command can become too long when trying to smoothly rack focus. ie during my tests with the 20mm 1.7 if you use "fast wide / fast tele" there is some hiccups between each occurrence of the command, if you use "slow wide / slow tele" there is no hiccups, but it's really too slow (because you are limited by the number of command the GH3 can process in a second, max is around 10/s). With other lens, I'm pretty sure you can fine tune and have a decent wifi follow focus program.
  • @lenuisible

    To make it work we need to make some simple command that can work more direct, I think.