On this lynda tutorial (part of a longer series of videos), Richard Harrington and Robbie Carman talks about some challenges and issues that need to be considered when shooting video with fast prime lenses.
The are a lot of things to consider when shooting with fast prime lenses and even more so when using lenses build for stills shooting for videographic work. One example is the smoothness of the aperture ring (many stills lenses have aperture rings that click when changing stops). The size of the lens is another consideration – small body with a very large lens can be unbalanced (there are ways around this like using a rail system but its good to keep in mind).
The most difficult thing that has to do with shooting wide open with fast prime lenses is the super shallow depth of field. If you are shooting a moving target especially in an uncontrolled environment it can be very hard to get perfect focus (sometimes even impossible as your subject will never be in full focus anyway). The answer to this is typically to close down the aperture and this is exactly what many professional videographers do.
You can find many more videos covering HDSLR techniques on our dedicated HDSLR tutorial section here on LensVid.