A note on Dynamic Range by Dan Hudgins

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  • #700

    Arooj Azam

    The dynamic range is the same more or less no matter what ISO you use with analog gain set to 1x, its the amount above or below 18% gray that changes.

    If you are shooting under controlled lights, you can get cleaner images shooting at 250! to 320! since you trade more room at the top, for more room at the bottom moving the skin tones out of the foot of the curve up into the “cleaner” upper stops.

    You should test the noise levels at 4K, I have been using the 2K camera which is maybe 12db less noise than shooting 4K mode, although if you reduce the 4K frames to 2K or HD with the kind of re-size that averaged the data, then sharpen AFTER reduction, you can get lower noise levels and smoother tones.

    That’s why the say its an 800 camera since that gives enough head room that you don’t burn out things most of the time.

    Turn on the zebras to make sure you are not clipping the sensor, the zebras work on the RAW waveform, so tell if if something is clipped in the recording, rather than just in the monitoring Rec.709 world.

    If you do not zebra the raw data and record DNG, you are safe and can fix things later by changing the ISO digital gain in post.

    I cannot sell a free program, and no mac version, although you can maybe load Ubuntu on a junk computer. My de-Bayer is of good quality, but can take 30 seconds to minutes per frame depending on how many filters are active, but for a short project like a music video that might make sense.

    DANCINEC.ZIP will support 3D-LUT cube files in the image processing in v0.1 but I am not sure when that will be released, I am still working in it and testing now. v0.09 is up on my web site now for beta testing.

    Speeds between 640 and 1280 with green analog gain set to 1x are general safe for most subjects, 2560 is only for when very high contrast subjects are needed, like night shots with bright window displays, since it moves mid-tone close to the noise floor, slower speeds down to 160 are useful for very soft and controlled lighting, speeds under 160 are not useful for general subjects because the will clip even minor highlights above 90% white.

    With the DNG you have a wide range of exposure correction, same with the Cineform if you by-pass the 3D-LUT, but then you have some issue with the color matrix as the sensor data is not symmetric so if you increase the saturation without the right matrix (which comes from the LK5 to the 3D-LUT in each shot folder) you get primary colors that are both over and under saturated at the same time.

    Yes, KineLOG 1280 is a “safe” choice and you can “over expose” a bit as long as you are not doing raw zebras and grade down later to reduce the shadow noise.

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