Computing absorbance for photometry
Absorbance A is related to Transmittance T – Standard expressions below:
It is intensity light exiting cuvette
Io, intensity of the light entering the cuvette
Transmittance (T) = It / Io == read/blank
A = – log10 T or A = log10 (1/T)
A = 2 – log10 %T
Programming Language Expression
A_1 = log((float)x1a/(float)x2a)/(log(10)); //calculate the absorbance green
A_2 = log((float)y1a/(float)y2a)/(log(10)); //calculate the absorbance blue
C++, log() is the natural log function. division by log(10) converts A to a log base 10
This code from b.y. inverts transmittance to get a positive Absorbance number but uses the natural log function.
log10(1/T) would do the same thing.
greenAbs = math.log (( greenBlank/greenRead))/(math.log(10)) # green
blueAbs = math.log (( blueBlank/blueRead))/(math.log(10)) # blue
A = math.log10(blank/read) # replaces the above
New in version 2.7.
math.log(x[, base]) With one argument, return the natural logarithm of x (to base e).With two arguments, return the logarithm of x to the given base, calculated as log(x)/log(base). Changed in version 2.3: base argument added.
math.log1p(x) Return the natural logarithm of 1+x (base e). The result is calculated in a way which is accurate for x near zero.
New in version 2.6.
math.log10(x) Return the base-10 logarithm of x. This is usually more accurate than log(x, 10).
T = blank/read
A = log10(1/T)
several log functions are available in excel