stephen

Some say there is a half stop light loss with the converter. So the lens becomes f/3.2-3.5. Which seems very logical and reasonable to me. But interestingly GH2 still displays aperture f2.5 with the converter.  Maybe the lens tricks GH2 to believe it's a f/2.5 while it is f/3.2 ? But there is no change in histogram and exposure parameters with and without the converter. Don't see the light loss in the LCD or viewfinder too. So don't know what to think but let's be realistic and say there will be some half stop of light loss, even GH2 doesn't detect it. 

This is what I call the poor’s man wide angle lens for BMPCC :)   Currently use it on my GH2 and it will work even better on BMPCC. It’s a 14mm Panasonic lens + Wide Angle Converter.  In my case Sony VCL-ECU1 converter instead of the original Panasonic one. When I bought mine Panasonic one was not available yet. Learned about this strange combo on a forum a year ago. With the converter image is probably slightly less sharp in the extreme corners but still perfectly usable and OK for me. Much better than what I typically see from C Mount lenses. And it will be even less of a concern for video. There is some distortion but still acceptable for me. Fairly compact, light and relatively fast as f2.5 is retained with the converter  Don't know how they do it but there is no light loss. On BMPCC  14mm will become a nice bi focal lens - 40mm and 30mm at f/2.5 (0.75 conversion ratio ) Not bad for 350$ that paid for the combo. On BMPCC extreme corners will not be visible as the camera will use only the central portion of the 14mm lens frame. Distortion and slight blur in the corners will be pretty much gone. I am satisfied with this solution on GH2 and it will work even better on BMPCC. It's not the fastest lens but with GH2 on ISO 1600 it works in most of my low light shooting scenarios. On GH2 it’s the equivalent of 22mm lens and I rarely go that wide on video.  Interestingly Sony converter clicks on 14mm Panasonic lens and it’s fairly stable.

IMHO the exact ratio of BMPCC to Full Frame is 2.88 Full Frame Active sensor area for full HD video is 36 x 20.25mm diagonal = sqr(36)+sqr(20.25)=sqrt(1706.0625) = 41.30 BMPCC active sensor area 12,48 x 7,02 mm diagonal = sqr(12.48) + sqr(7.02) = sqrt(205.0308) = 14.3189 41.30/14.3189 ~ 2.88 Which is the same if you simple divide the long sides - 36/12.48 ~ 2.88 Most C-Mount lenses cover 2/3'', 1/3'' and 1/2'' inch sensor sizes. Probably only 10 to 15% of all C Mount lenses cover the 1'' sensor size needed for BMPCC. So most will vignette heavily on BMPCC and among those which do cover correctly the 1'' sensor size there may be still problems. Like: 1. Will the lens work without modification on a C- Mount to m43 adapter. Some don't. Can't focus on infinity and need some rework. 2. Is the image quality good enough. Most of those are surveillance camera lenses not optimized for high quality photo/video/film work. From what I've seen image quality on GH2 (tele converter mode) doesn't look good. It doesn't make sense to buy BMPCC which is supposed to give great image quality and stick a poor soft lens in front of it. My hopes are in Metabone Speedbooster for m43.