Nikon 9235 Reference Manual - Page 68

Step 3-Setting the White Point and Black Point The endpoints of the curve are referred to as the "white point" and the "black point." The black point for a given channel represents the darkest shade (minimum value) for that color, the white point, the brightest shade (maximum value). In the CMYK color model, the black point is at the right end of the curve and the white point at the left, while in all other color models the white point is at the right end of the curve and the black point at the left. White-Point and Black-Point Input Levels Input levels for the white point and black point can be set using any of the following three methods: • automatic contrast adjustment • white-point and black-point sliders • direct sampling using the white-point and black-point eye- dropper tools By default, the input and output values for the black point are zero. The darkest shade in the input image may however be greater than zero, with the result that a portion of the curve is dedicated to reproducing tones not actually present in the image. Increasing the input value for the black point until it matches the darkest shade in the image will steepen the curve, enhancing overall contrast without causing a corresponding loss of detail in shadows. Similarly, if the original image does not actually contain shades corresponding to the maximum value, the white point can be lowered to match the brightest shade in the image. There are two steps to selecting a white point and black point for the final image: choosing the white-point and black-point input levels, and selecting output levels. Reference:The Tool Chest 67