Follow Focus Using In-built Lens Motors
 

View Factor have this new follow focus coming out next month (Impero HDSLR Controller) that plugs in to the camera's USB port and allows you to pull focus using the AF motors that are built into Canon's lenses. Looks like a great solution particularly if you are trying to keep your rig compact.

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Clearly they are tapping in to the same protocol that allows you to control your camera (including focus) via your PC.

As an aside if you plug your camera in to your computer and have a play with the focus controls you'll notice that there are three speeds at which you can alter the focus. The faster two produce noticeable jumps in focus rather than a smooth racking. The third speed produces super-slow (in fact almost imperceptible) changes in focus. I guess the Impero mustn't be limited to those speeds otherwise it wouldn't be very useful as a follow focus.

I'm looking forward to seeing some reviews of this product when it comes out to find out just how smoothly focus can be pulled using the lenses AF motors.

That's freaking fantastic! Wonder why no one hasn't thought of that before..?

-- peer

i used that long ago with LanC controller, but you can find how it is limited very fast.
no speed control.

Yes I agree. I guess the elegant solution to any problem always does seem kind of obvious (at least once someone has thought of it). Then again the elegance of this solution depends on how well it works. As I said I'm really looking forward to finding out.

I think the cool thing is that if this system does work more-or-less-effectively, then your gonna see other peripheral manufacturers fall over themselves to produce similar products. Some that will probably be cheaper than the 500 dollar View Factor version and others that might be more expensive and more sophisticated.

I would suggest that the limits of that approach were more about the controller (not designed for FF) rather than the focusing motor. The fact that you can produce smooth racks in Magic Lantern combined with the fact that the sort of control required for a FF is really not that sophisticated (I have done similar things with individual stepper motors myself, and I have little knowledge of electronics and programming) makes me think this is an entirely plausible mode of focus control. Having said that we'll just have to wait and see when the product comes out.