Hi, I am brand new to APUG and to large format photography. In fact, my Pacemaker Speed Graphic just arrived yesterday. There are some terms I am unfamiliar with and I was hoping someone on this forum could help. There was a gorgeous photo on Flickr I really liked (http://www.flickr.com/photos/ulvo/4291950562/) In the description it said:

Fomapan 100 @ EI 50 (over-exposed by one stop)

I know the film, but I'm unsure if EI means exposure index??? And how does one get EI 50 on a Speed Graphic? This isn't Aperture or Shutter speed, is it? I'm so sorry, but I really don't get what they mean and I've been seeing EI a lot!! I'd really appreciate it if anyone who would be kind enough to shed some light on what this really means and what they're doing. Even enough so I can continue my research......thanks!