There are a few steps to determining the value of flare. The first step is to find the exposure for the shadow. This equation is the first equation in the upper left of the example. The example uses a subject luminance range of 2.20 logs with the diffused highlight starting at 100% reflectance. That means the shadow RD is 2.20. The next step is to determine the flare value. I’m using a flare factor of 2 or 1 stop. A one stop flare factor value of flare will equal the value of the shadow exposure. This value is then added to each calculated value of exposure.
In the example, the actual nomenclature for Es and Ef should be Hs and Hf. I wanted to use separate symbols for the flare exposure in order to an attempt to minimize confusion.
Exposure Equation example w flare.jpg
Flare has effectively doubled the shadow exposure at RD 2.20. It has gone from 0.0034 lxs to 0.0068 lxs with the addition of flare. This brings the shadow exposure up to the exposure for Hm. Without flare 0.0064 lxs would occur at an RD of 1.92 which is a touch under one stop difference.
How does this look plotted?
Plottiing Example with flare.jpg
Matched to the film curve.
2 Quad - Exposure example w flare.jpg
And comparing the resulting negative densities from the no flare and flare examples.
Negative Density Comparison.jpg
Last edited by Stephen Benskin; 05-13-2013 at 10:30 PM. Click to view previous post history.