Let me say ahead of time that I come from a broadcast background, and I am just dipping my toes in the world of RED, so please excuse any gross errors I make in my reasoning/questions.
I have seen some comments on using 18-80 with an EPIC, but nothing about the 45-250. The quality of the glass and mechanics aside, the first thing I need to find out is whether the lens gives full frame coverage of the 5K EPIC sensor. The specs from ARRI indicate that it has an image diameter that will cover at least DIN Super 35 (30.0 mm), but the EPIC sensor at FF 5K is slightly larger (27.65 x 14.58, ID ~ 31.26 mm, I believe). Can anyone confirm that they have used this lens to shoot FF 5K without vignetting?
I am also interested in pairing a PL doubler/extender with the 45 - 250. The ARRI-Fujinon brochures indicate that Fujinon has new extenders specifically for the Alura's (Fujinon Zoom Extender 2.0x - K2.47927.0), but I have not been able to locate them anywhere except in the brochure. Has anyone used/located these? If not, can you recommend an alternative PL doubler? Will the 2x ARRI Extender work?
My understanding of the geometry of the situation is that if a lens fully covers the sensor, then there should be no problem with coverage when adding an extender. The only issue I can imagine would be if the housing or entrance pupil of the extender were designed specifically for a typical 35mm target and thus were small enough so that they cropped the incoming image. Is this accurate? If so, can anyone confirm a specific doubler they have used that still provides full coverage of the full frame 5K sensor?