Split Toning is an effect which has its origins in the days of film and it involves tinting the highlights in a black and white image one color and the shadows another color. The best results are where you use opposite colors for each, such as yellow and blue, green and magenta and so on.
The bleach bypass effect has its roots in the traditional darkroom. It’s a complicated and potentially messy process that requires the printer to miss out certain chemicals in the printing process. However, the striking results boast enhanced contrast and wonderfully muted colours that are generally considered to be worth the effort. It’s easy to see how the technique has become extremely popular, especially with advertising and fashion photographers.