What Source Did You Use?

I've been working on an early Tennessee family lately and using marriage records as a part of my research. There are many ways I can access those marriages, but I need to think about what source I am using. Am I using:

• Original paper copies
• Microfilm of the original paper copies
• Digitized images made from the microfilm
• Published transcriptions
• Handwritten copies made from the originals

One of the many questions is, if I am using those published transcriptions--were they made from the original paper copies, the microfilm, or the handwritten copies made from the originals. Transcriptions can always have the occasional error, being made by humans. Transcriptions made from transcriptions have an even higher liklihood of an error. And there is always a chance something is transcribed incorrectly or omitted.