Alister Chapman, Cinematographer, DIT, and Educator – Personal Website

Uncompressed 240 fps possible with FS700 and Convergent Design Gemini. Tested!

Using Convergent Design Gemini to capture the 50p buffer stream from a Sony FS700

Great news. I was able to confirm yesterday that it is possible to record the super slow mo buffer stream from the Sony FS700 to an external recorder. When you shoot Super Slow Mo with the FS700 the camera buffers the slow motion footage into an internal frame buffer before reading this frame buffer out and encoding it to AVCHD to write to the internal compact flash card. The footage is read from the frame buffer at 50/60p depending on which country area the camera is set to.

Setting up the output.

The cameras output can be set in the menu to either 25/30p or 50/60p, if set to 50/60p the HDSDi output is 3G. In either case the buffering happens at 50/60p. So FOR THIS TO WORK CORRECTLY THE RECORDER MUST BE 3G CAPABLE AND BE ABLE TO RECORD 50/60P, if the camera output is set to 25/30p you only get one field from each frame in the buffer stream on the output Sdi at 1.5G. So you end up with a slow motion interlace video stream with recorders that can only record up to 25/30fps. The end result of this is that if you shoot at 200 fps with the camera output at 25p you would end up with an external recording the equivalent of 100 fps with a 180 degree shutter. Every external HD recorder that I know of can record this as it is nothing more than 1080p25 (or 1080p30). A very useful and a nice option. To get the full benefit of external high speed recording you need to set the FS700 to output 50/60p over 3G SDi and then you must use an external recorder that has 3G SDi and can record at 1080 50/60p, something like the Convergent Design Gemini. Using a 50/60p external recorder you can then record every frame from the frame buffer. If you then take this 50/60p recording and slow it down by 50% in the edit suite you end up with full HD resolution, uncompressed 200/240 frames per second video. Very impressive indeed!

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