I managed to get hold of one and use for 3 weeks last month. Absolute joy to work with, so much so that I will be switching to it from my f-line metric. In fact, I will be switching to the RL3D, so that I can have tilt or swing without having to rotate the camera, and also a 5-10mm extra shift movements.
I was at the factory with Marc last year and had a quick play with them. The RL3d is actually only about 1 inch bigger in size. I was looking at the m-line two for a while, and perhaps if funds allow then I will get one of those somewhere down the line. The R-line cameras are such a great way of working on location, very good for interior work I found, and for landscape work you can find infinity in no time. I generally shoot untethered, only doing so with lighting setups. I also found that the once the DB is on, its just stays on and you just switch lenses and shoot...pretty much!
So, I've got an f-line metric for sale if anyone is interested. exactly one year old. I'm based in London.
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