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Re: Sigma fp

Re: Sigma fp


Daniel Rozsnyó
 


On 12/27/20 3:26 AM, Mitch Gross wrote:
Because uncompressed RAW means huge files that take up a lot of disk space, take a lot of time to transfer, and require considerable computer power to deal with. But with Log encoding you get the vast majority of flexibility in what the sensor can capture but recorded in a data scale that is reasonable enough to everyone to work with. Clients won’t complain about the data load and the work can happen quickly and effectively.


Sorry, but having LOG does not mean "huge compression" at all. Maybe you mix up things - like you bring in also AVC or HEVC to the process, those ones have such poor bit depth (8 or 10bit), so the only way to feed a wide dynamic range picture to these codecs is to apply a LOG conversion.

For me a LOG format compared to LINEAR is anything with missing codes - basically a LUT to convert from more bits to less bits. Like from 10 to 8 or from 12 to 10, or from 14 to 12. And that saves about 20% of data rate, in "uncompressed" form. Because LOG is not just a mapping scheme, but also a very simple and lossy compression (you are not able to recover the linear original, some posterization will happen).

Most of the BMD cams, which resolve more than 12 bits (eg. by a dual-gain readout) apply such log conversion silently even for the DNGs - (where the feature is called LinearizationTable), but in the rare case of the dual-gain ADC readout, there was never a linear range form, that would contain all the shades - basically the 11+11 bit reading, that covers 14 stops thanks to the 3 stop separation, is loss-lessly storable in a 12 bit form (1 bit to tell whether the shade is within the low or high gain, and the 11 bits of that gain).

So again, please do not mix apples and oranges. LOG is not related to huge compression. H264 and H265 are the ones to blame for the convenience of small files!


You are also wrong on the need of computer power - the uncompressed footage will be ALWAYS easier to process than any of the AVC/HEVC ones (try to render a clip with reversed time..). Drive capacity/speed or network bandwidth sure needs to be adjusted - I see no problem here, we have multi-gigabit SDI for two decades, and you still complain to not have enough power on your pocket calculator. Upgrade your gear, its doable.


The whole issue with uncompressed workflow (or the thing which killed it at classic vendors) was the absurd price of branded media, an even more absurd ratio of performance/price, which then resulted either in inability to keep up with the bitrate, or limited the usability because the low capacity was for silly short takes. Devices which offer recording to any media do a lot better job here.



Ing. Daniel Rozsnyo
camera developer
Prague, CZ

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