Hi Rafal,

Thanks, it's nothing...

Here is the graph.

Shows how difficult curve fitting can be, where the goal is to find one number to represent the curve.

The "c" marks I drew on the curves are the points I used to give Contrast Index (CI) estimates.

Small diamonds are the 0.10 "speed" point (small diamonds to the right and above are the corresponding ASA triangle aim points). The larger double diamonds (kind of looks like a dream catcher) emphasize that you exactly hit the ASA triangle at 11 minutes.

Drawing a straight line, ASA triangle is 0.62 CI. But ASA aims for different points on the curve than CI. The 11 minutes curve is 0.75 CI by my estimation. Crazy. Shows how badly a single number fits the curves.

Also shows how much tolerance there is. A good argument can be made to choose anywhere from 7 to 11 minutes as Normal. I think 6 is a bit short side but have to agree it's close.