I wanted to make a simple method for approximating bellows extension exposure compensation. Maybe just a string with 1/2 stop marks on it, attached to the rear standard that could be drawn to the front standard to read out the compensation.

I focused my 150mm Rodenstock Geronar at infinity and measured the the distance from the glass to the shutter. It was close to 5.2". Nowhere near the 5.9" that I had expected.

Can someone give me a reality check? Should I figure my compensation based on my measurement or on the marked F.L.?