check this in project setting under General option
Use S-curve for contrast: On by default, this checkbox sets the contrast control in the Color Wheels palette to apply an “S-curve” to the image, such that the shadows and highlights of a signal will not be clipped when you increase the value. If you would prefer for these contrast adjustments to be made linearly, and for the signal to be allowed to clip when you reach the upper and lower boundaries of the video signal, you can turn this checkbox off.
Davinci resolve 16 refrance manual page 165