A video signal mixer with a parabolic signal mixing function, especially useful in scene-by-scene color correction systems and “blue screen” video masking applications. The mixer effects mixing two independent signal sources while smoothly controlling the rate of change during mixing. An input stage receives a first video signal and a second video signal. The mixing circuit mixes the first video signal with the second video signal based on a predetermined parabolic function. An aperture signal circuit in the mixer allows a degree of operator control over the parabolic function. An output stage provides a parabolized output signal. The output signal, which comprises the mixture of the first video signal and the second video signal, eliminates discontinuities in regions of the signal which would otherwise produce discontinuities in prior art types of video signal mixers.