NEX-FS700 8 Bit video but 12 Bit RAW in 4K, 2/3″ lenses using center crop?

Sony NEX FS700

The more I think about this camera the more exciting it becomes. At release the FS700 will be limited to HD and in many respects will be similar to the FS100. This means that although the FS700 has a 3G capable HDSDi output, when in video mode this output is still restricted to 8 bits due to the internal video processing. However from what I have been able to gather, the proposed 4K mode bypasses this processing altogether and outputs the direct sensor data as 12 bit RAW sensor data. How is this possible? Well any video camera outputting video has to output 3 values for every point within the image. So for a 1920 x 1080 camera there are in effect 3 outputs, one for the luminance value for each point plus two chroma or colour values, one for Cb one for Cr. In a 422 system the resolution of each of the Cb and Cr channels is half the full resolution, so that’s 960 x 1080 Cb and 960 x 1080 Cr. However you look at it that’s a lot of data, even at only 8 bits, but 422 1920×1080 8bit and even 10 bit 422 will fit into a standard 1.5G HDSDi signal. With a 3G HDSDi connection the amount of available data bandwidth is doubled. This in itself gives the ability to transfer 444 HD data with full R, G and B data or Y, Cb, Cr at full resolution for each channel at 8 or 10 bits (FS700 restricted to 8 bit processing).
With 12 bit data however, at 4k there would not be enough bandwidth, even with 3G to transfer a 444 or even a 422 video signal, the extra 2 bits of data needs a lot of extra bandwidth. But Sony are not talking about video data, they are talking about RAW sensor data. The sensor in the FS700 is a bayer sensor. A bayer sensor has an array of pixels with colour filters over the top of the pixels to filter only green light to every other pixel and red and blue light to the remaining pixels. The pixels themselves don’t see different colours, all they see is a brightness or luminance value. It’s not until the luminance data from the sensor is processed (de-bayered) that the colour information is created by extrapolating luminance (brightness) values from the R, G and B filtered pixels. The De-Bayering process creates an R, G and B value for each point in the 4k image, so 3 values for each point. However if we just take the RAW luminance values all we have is a single luminance value for each pixel on the sensor. The De-Bayer process ¬†greatly increases the amount of data that needs to be processed, keeping the data as luminance only minimises how much data there is and makes it possible to pass 12 bits of 4k data over a 3G HDSDi cable.
Now, this signal from the FS700 will not comply with any standard that I know of, so it will need a dedicated recorder or at least a recorder programmed to accept it, but it promises a lot of exciting possibilities.

For a start, you will get the full sensor dynamic range, so we should expect at least 12 stops of DR, maybe a bit more. In addition having a 4k image means that when shooting for HD you can crop in to the image with no resolution loss. Here’s a thought, you should be able to use a 2/3″ ENG broadcast zoom. Yes the image on the sensor will vignette, but you should be able to extract a full 1920×1080 resolution image from the centre part of the 4k image. As this will be using a smaller part of the sensor your DoF for a given field of view will be similar to what you would have with a 2/3″ camcorder. So could the FS700 be that jack of all trades camera many of us are looking for? 4k RAW, s35mm when you are making a filmic piece and then with a simple lens mount adapter (no optical elements needed) stick an ENG zoom on it and use it for news style shooting. At the moment it looks like you will have to extract the HD 2/3″ centre crop from the RAW 4k yourself, but perhaps Sony will be able to add centre crop to the camera firmware at a later date.
However you look at it, the FS700 is a very exciting proposition. I placed my order for one the day it was officially announced.

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