With the exposure formula in hand, we can now work out the range of film plane exposures (H) for the average scene luminance range. The range is measured from a diffused white containing some semi-specular highlights which has a reflectance of 100%. The range is 2.20 logs.
Exposure Equation 05.12.jpg
The aim exposure at Hg for a 125 speed film falls at a reflectance of 12%. The value of L define in the exposure meter standard confirms this exposure (the numbers are slightly off here probably because of rounding). An exposure at Δ1.0 logs below Hg equals the aim value of Hm = 0.0064 lxs for a 125 speed film. The shadow exposure falls approximately Δ0.30 logs below Hm.
This can be plotted.
Plotting exposure 2.jpg
Last edited by Stephen Benskin; 05-12-2013 at 04:51 PM. Click to view previous post history.