Film Analysis
Select the “Analyze” tab and you’ll see the curve family displayed without
the grid pattern. The program will have established the approximate location of
the ISO speed point, as indicated by the large dot on the x-axis and the dotted
vertical line extending from it. Also, if one or more of the curves’ slope (or
gradient) is too low to accommodate your chosen ES (Exposure Scale) value, the
program will have extended the curve(s) with a dotted line. This extended
contour is not entirely reliable but it does attempt to represent the average
behavior of typical film curves as exposure is increased beyond the usual
limits.
Click on the “Display Information” check box to see the dotted triangle that the
program uses to locate the nominal ISO point. It will appear as a small gray
circle on the x-axis. If you have enabled the ”Personal Speed Point” and
assigned it a value in the “Options” window, a dark, combined dot/triangle will
mark its location on the x-axis. This point (instead of the nominal ISO point)
will be used as the reference for calculating the Effective Film Speed (EFS)
values of the individual curves. Next you will see each of the curves
labeled with its Effective Film Speed (EFS), its Average Gradient (G-bar), and
the Subject Brightness Range (SBR), as determined by your choice of the ES
value. If you change the default ES value, you’ll see some of these other values change as the program recalculates
them.
You’ll see similar changes if you select “0.1 over FB+F” instead of the
default “Approximate CI” speed point location. You can also add a “Flare
Density” value to see how simulated flare affects the curve contours and their
data. Flare densities of from 0.001 to 0.1 are reasonable; a realistic value for
general viewing is about 0.02.
To simulate the effect of exposure variations, enter some stop value in the “Exp
Adj.” field. A positive value simulates overexposure; a negative value provides
an underexposure effect. For a change of less than one stop, enter a decimal
fraction. All of these adjustments can be applied when either the entire family
or a single curve is displayed.
If the opening window is too small to include all of the information panel at
right drag the lower right corner of the window down until the entire panel is
visible and the curve display will be scaled up to fill the new space.
The Paper Analysis screen is similar to the Film display but it offers a
“IDmin %” option. The default value is 90. This number establishes the maximum
usable print image density (90% of Dmax), as defined in the ANSI/ISO 6846: 1992
Standard. You can change this value if you want to but if you do the calculated
ES and paper grade numbers will no longer conform to the Standard and can’t be
compared realistically with the paper manufacturers’ published data.
When you select a single curve you’ll see it displayed with the construction
lines that define the curve’s useful density limits (IDmin and IDmax) with their
values labeled. A vertical line intersecting the curve at the 0.6 density level
indicates the paper’s relative sensitivity, which the ANSI Standard and the
paper manufacturers express as ISO paper speed; e.g., ISO P100.
The paper’s Density Range (DR) is the difference between IDmin and IDmax
measured on the y-axis; the ES is the difference between IDmin and IDmax
measured along the x-axis. The ES value—rounded to the nearest tenth, then
multiplied by 100—becomes the ISO range number, which is a somewhat more precise
indication of the paper’s inherent contrast characteristic than the conventional
grade numbers are.