Apple’s Color, as part of the Final Cut Studio, is going to be able to bring professional quality color correction tools to your project. Most people think that if they do not need this level of color grading then they can just use the 3-way color corrector video effect in Final Cut Pro, but in reality this is still not often going to be what you need. Beyond this, if you simply want to change your film to black and white it seems as though the simple desaturation tool in Final Cut Pro will do the trick. If you have to transfer a film that is shot in color to black and white you are going to encounter a lot of issues around contrast as well as light and dark areas. To really address what is needed you are going to want to do all of your color work in Apple Color, including desaturation. Here is a basic tutorial on how to add this simple desaturation to your video in Apple Color.
Apple Color does not approach color grading as an effect that is added, but instead gives you a series of tools that let you alter the color of the image in a variety of ways through full creative control. What this essentially means is that you do not just hit a switch to desaturate an image. Instead, what you will do is adjust the basic saturation of that image until it is desaturated to the point that you would like, which very well may mean taking it all the way to black and white.
Once the clip has been sent from your Final Cut Pro Timeline to Apple Color and the clips are up and running and it is under the playhead. Look over at the image and its Overlay waveform to see where the color is at. Go to the
upper right hand corner of the Primary In tab and you are going to see a number of options starting with Saturation and leading to Highlight Saturation, Master Life, Master Gain, and Master Gamma. The Saturation starts out at 1, and it can go up or down from there. To fully desaturation the image you can just highlight the number that is there, delete it, and enter zero. This will turn the image into a clean black and white as it will have been completely desaturated. You do not have to do this entirely as you can also just use some desaturation by entering a number less than one, with the closer to zero you go the closer to a black and white grade you will head to. You will then do this with all the clips that you want to change to the desaturated mode in Apple Color, or copy and paste the grade between them.
What you do after the desaturation in Apple Color, if you are using complete desaturation, is the real color grade for you. Instead, this may be where you raise the contrast by using the Master Life and Master Gain, change brightness, or really do a whole list of things. You will not know exactly how to grade the image until you can look at the entire thing in black and white in Apple Color.