Sunday, 6 September 2015

Adding follow focus to the Lumix GH1 (DSLR camcorder build - Part 7)

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I'm still figuring out the Lumix GH1 project. I've made a few small adjustments to the position of things on the home-made rig and just added the follow focus rack. This is one of those situations where photographic cameras and the movie camera business diverge, but a fairly simple change could make quite a difference.

Movie camera lenses are (a) expensive (b) manual (c) don't have many of the last 15 years of consumer advances incorporated, such as image stabilisation.

However, a major mechanical difference is that movie lenses have a gear built onto their focus ring. This allows a follow focus to be driven by an external wheel, and is the way that professional cameras (other than Electronic News Gathering) capture focus.

In order to implement this gearing on an SLR lens, there's a need to add a wrap around wheel with the gear teeth on it. In my opinion, it would be simple for manufacturers to build this into the original design of SLR lenses too, but I can understand why they don't.

A set of movie lenses consists of around 6 primes and for a modern set of Cooke would cost something like $60,000, or $10k per lens.

The lens above is a typical modern and brand new example, complete with a movie style bayonet mount. Notice the gears on the focus ring. Similarly, a set of Leica movie lenses will cost even more, perhaps $100,000. They also have the special gear teeth included.

I did check out the Canon set, which is a mere $30,000, although these use the Canon EF fitting instead of the standard movie one. Sure, these are fast lenses at f1.5, but maybe even these are outside of my budget.

That's where the plastic wrap around cogs and a zip tie come in.

My adaptation of a DSLR zoom lens cost about £6.

I know, it doesn't have the maximum aperture of the Canons or the Leicas, but it does fit straight onto my adapted m4/3 camera and work with the focus rack.

I'm nearly ready to try all of this in a few scenes, once I've put the matte box back on the front. The total cost so far is as follows:

So I'm up to spend of £86, so far. It would be good to finish the project for sub £100.
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