Poserframes attempts to analyze the visual black point in your image and then lift the blacks of the negative rebate to match. For some aesthetics the model used might result in too dark or too light rebates, but by using the setting adjust_blackpoint you can systematically adjusts this, so you for instance can have a more underexposed look. Having the setting halation as true adds a halation effect to the rebate, adjacent to bright pixels. The setting rebate_grain lets you add a fine grain to the whole rebate (set to true), or just to before mentioned halation added to the rebate (set to halation). If your image already has grain, I recommend using the halation setting, but if you intend to add grain after Poserframes I suggest keeping this setting as false.