Now we can combine the camera exposure with the film curve by aligning the camera exposures up with the sensitometric exposures. For this to work, the camera, the film curve is turned on it’s side. This can be disorienting at first, but it will soon become second nature.

2 Quad - Exposure example.jpg

For a film that has a speed of 125, the exposure of 0.0064 lxs falls on the 0.10 density speed point and 0.064 lxs falls Δ1.0 log-H above it. This is how the subject luminance range is connected to the film curve using just the film speed number and an exposure meter that wants to place everything at 8 lux, except there’s a problem with this example.

Upon a closer look, the shadow exposure doesn’t line up with the speed point. It has an exposure of 0.0034 lxs or almost a full stop less than the exposure needed to reach the speed point. Where the exposure of 0.0064 occurs, it does line up with the speed point, but it represents the shadow luminance at RD 1.92 and not the deepest shadowed measured at RD 2.20. What's wrong?