I did a brief test indoors just now. With the 7D and 17-55mm, I selected an aperture that gave a 1/30 s exposure, so the 10-stop ND should meter at 30 s. With the ND in place, the scene was way too dark to compose in the VF, AF did not work, and the metering sensor underexposed at 8 s. Live View with exposure simulation was still too dark to compose (Sean, I guess the full 10 stops exceeds the capability of the gain for the simulation, unlike the max density of the fader), AF still did not lock, but the metering off the image sensor was actually correct at 30 s. However, I should mention that I do recall trying this when shooting landscapes, and Live View on the 7D still underexposed.


Then, for kicks, I tried the same test with the 5DII and 24-105mm, at ~27mm so the framing was the same as 17mm on the 7D, and with an aperture set to result in 1/30 s exposure as before. Through the viewfinder with the 10-stop ND in place, the 5DII metered underexposed, more than the 7D at 5 s, and thus outside of the 2 EV exposure compensation range if one was shooting in Av mode. However, the 5DII