Posts Tagged ‘ctb’

New CTB (color temperature blue) filtering for the RedOne Camera


CTB (color temperature blue) filtering for the RedOne camera:

I love the idea of a filter purpose built to raise the color temperature/white point with as little light loss as possible. Several people have contended, some with a fair amount of test results to back up their assertions, that raising the CT makes for cleaner keys and better noise characteristics. Other have argued that when light levels are low it is better to keep every photon you can so that the red and green channels can provide grist to extrapolate the blue information.

From what I’ve seen there is an issue in terms of the “subjective noise awareness” factor of the viewer when the blue channel is starved and base level sensor patterning reveals. For this reason I advocate the “careful” use of blue filtering, especially in available light situations where the native CT may be less than 3000 Kelvin.

I would not give away a stop or more just to nail 5000K but I would, for example, give away 1/3 stop to get to 4000K. In a perfect world I would carry 3 filters of differing strengths designed specifically to compensate for the lack of blue sensitivity inherent in the current crop of CMOS sensors.

It is my belief that Graeme’s algorithms perform best when the inequality of the color channels is more moderate. This advice is based on tweaking a lot of underexposed footy in Scratch in full res, full debayer with an eCinema reference monitor. YMMV.

I am a big fan of Schneider filters and am stoked to see them jump in with CTB options. 80 series filters are designed to allow the use of tungsten balanced film stocks in daylight shooting. I contend this particular MIRED shift is based upon assumptions that are overkill for the RedOne’s Mysterium CMOS sensor and results in more light loss than necessary. I consider it silicon chip color response compensation and prefer a filter that does exactly that.

Thanks to David Mullen for helping me understand this issue.

Blair S. Paulsen
4K Ninja
San Diego

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