For years I used this equation with a 'room temp.' method. The equation is taken from the Kodak darkroom dataguide. I remember using my first computer (Commadore 65) to decode the Kodak wheel back in the 80s. Later I put the equation into an Excel spreadsheet.
New Decimal Time=((X_Constant*($B$6-(Temp * Y_Constant))/(1+(Temp * X_Constant)))+Y_Constant)*(LOG(A9))+($B$6-(Temp * Y_Constant))/(1+(Temp * X_Constant))
x_constant =-0.6205672
y_constant = -0.576929
$B$6 = base time (min)
Temp = base temp (degrees)
A9 = new temp
To convert to minutes and seconds:
Minutes and seconds =INT(decimal time[-1]) + ((decimal time[-1]-INT(decimal time[-1])))*0.6
(working spreadsheet available to anyone who asks) |