#!/usr/bin/gnuplot

# Method for determining the speed of a black and white film
# as per ISO 6.

f(x) = Dmin + (Dmax-Dmin)/(1+1/x+1/x**3)
D(x) = f(10**((x-offset)/stretch))
Dmin = 0.2
Dmax = 2.7
offset = -1.161
stretch = 2.775
x_m = -2.38851
y_m = Dmin + 0.1
x_n = x_m + 1.3
y_n = y_m + 0.8

set terminal svg size 640 480 enhanced dashed
set output 'Black_and_white_ISO_speed.svg'
set xlabel "log H"
set xrange [-3:1]
set xtics ("−3" -3, "−2" -2, "−1" -1, 0, 1)
set ylabel "D" offset 1.5, 0
set yrange [0:2.5]
set ytics 1
unset key
set label  1 "Δ log H = 1,3" at x_m + 0.65, 1.5 center
set label  2 "ΔD = 0,8" at -0.66, 0.7 center
set label  3 "ΔD = 0,1" at -1.27, 0.46 center
set label  4 "m" at x_m - 0.08, y_m + 0.09 center
set label  5 "n" at x_n - 0.08, y_n + 0.09 center
set label  6 "D_{min}" at -0.4, Dmin center
set label  7 "log H_m" at x_m, -0.12 center
set label  8 "D_m" at -3.16, y_m + 0.02 center
set arrow  1 from x_m, y_m + 0.05 to x_m, 1.6 nohead
set arrow  2 from x_n, y_n + 0.05 to x_n, 1.6 nohead
set arrow  3 from -2.10, 1.5 to x_m, 1.5 filled
set arrow  4 from -1.37, 1.5 to x_n, 1.5 filled
set arrow  5 from x_m + 0.10, y_m to -0.7, y_m nohead
set arrow  6 from x_n + 0.05, y_n to -0.7, y_n nohead
set arrow  7 from -0.8, 0.62 to -0.8, y_m filled
set arrow  8 from -0.8, 0.78 to -0.8, y_n filled
set arrow  9 from -3, Dmin to -0.55, Dmin lt 7 lc rgbcolor "black" nohead
set arrow 10 from -1.3, Dmin to -1.3, Dmin + 0.1 nohead
set arrow 11 from -1.3, Dmin - 0.01 to -1.3, Dmin size 0.07, 15 filled
set arrow 12 from -1.3, Dmin + 0.11 to -1.3, Dmin + 0.1 size 0.07, 15 filled
set arrow 13 from x_m, 0 to x_m, y_m-0.05 nohead
set arrow 14 from -3, y_m to x_m - 0.10, y_m nohead

plot D(x) lw 2 lc rgbcolor "#00007e", \
     '-' w points ls 7 lc rgbcolor "#000000"
-2.38851  0.3
-1.08851  1.1
e