I picked up a Voigtlander Bessamatic Deluxe this week with a 35mm, 50mm, & 135mm. How does the meter work on this camera. I can see the setting for the DIN/ASA which I can change but how does that relate to the EV and the f-stop and shutter speed? It also came with a Telex that fits onto the top of the camera's shoe. What is a Telex and how does it work?