There are some good documentary movies out there if you are interested in knowing more about BDSM. One that I would like to promote is BDSM – Alternative Loving, a full length documentary movie which includes interviews with famous people, like Gloria Brame, from the scene. The documentary is 107 minutes long and a good introduction to what BDSM is about and the variety within it.
Some years have passed since the documentary was made, but the subject is still relevant and the insights into the scene are still valid.
You also get extra stuff with it, a kink test and BDSM art is some of the things. Have a look at the preview down below, it might be something right up your alley.