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Extend focus throw with gears?

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  • Extend focus throw with gears?

    Hey guys,

    I'm looking to get the Sigma 17-50 2.8 OIS as a cheap yet decent zoom. My concern is with the quite short focus throw, is it possible to have a follow focus set up that would extend it some what and is it worth the gain?

    Also any first hand experience with it on the micro cinema camera would be awesome.



  • #2
    I've used that lens on the bmmcc, and in general on a few other cameras. It was my first zoom lens I ever bought. It's an excellent stills lens, kind of bad cinema lens. Treat it like multiple primes in one and you won't be disappointed. No way around the short throw. Expect to get familiar with it so it's muscle memory if you want to do anything technical. The short throw actual helps a bit as a solo operator, a light touch from one hand is all you need. It also has heavy focus breathing and the focus shifts quite a bit when zooming. If you use it heavily you will get all kinds of dust and particles inside because of the barrel design. For the price though it's more of an expense than an asset if you get my meaning. Mine has become my "beater" lens that I put on in dusty, harsh environments. I've dropped it more than a few times and only broken filters, it's pretty robust for being mostly plastic.

    Just a heads up, with a metabones on the aperture opens so much that the focus field gets razor thin. If you're opening all the way then you better be locked off and your subject not going anywhere!

    The IS helps with handheld but don't expect to be able to get any walking shots or anything. I've been able to mimick a short dolly track by shifting my weight with this lens + 60fps, it's possible.


    • #3
      I'm looking at getting a grey market one for around 330 AUD which I feel at that price I could live with the mentioned downsides. I've noticed the thin DoF atm testing out the cheap Canon 50 1.8 because atm I only have the Hoya pro ND 64 and at 6 stops of reduction I'm having to shoot too thin to focus well. So I'm gonna grab the Hoya pro ND 16 at 4 stops along with the sigma 17-50 2.8, the OIS will help me on the longer end.

      Thanks for the advice.


      • #4
        You can add a larger focus gear with a small gear on thr FF to get more range of movement in the FF knob.


        • #5
          I used the Sigma 17-50 2.8 on the BMPCC with a Speedbooster for a doc and it worked fine. The focus throw was super tiny but it didn't cause any problems. In fact, it may have helped shooting as a one man band. For narratives I can kinda see it being a problem as you probably want a smooth focus transition.

          I have a set (3) of Cinevate lens gears and a Cinevate single handle focus lever I am selling. They are all new and were never used because I was shooting a doc while I had them in my possession. I am in South Korea at the moment so better than mailing them from the States. PM me if interested.