Before buying an Arca 6x9/4x5 FC, I was intrigued by the Brainbox accessory. Thi s mechanical aid offered to help measure and calculate "depth of field, extensio n and swing angle." This may represent Dumbo's Magic Feather for a LF beginner like me, but I'm curious. One dealer told me Arca has discontinued the Brainbox ; but B & H still lists it as a special order item for $235. My question is whe ther anyone has used the Brainbox, knows how it compares in convenience and accu racy to Sinar's near-far focusing system, and whether it is or is not available.