With a densitometer:
1. measure the 100% Light Black patch: Density 1.29
2. measure the 40% Black patch: Density 1.22. I selected 40% by eye,
but you can use the densitometer to find the darkest patch with
density less than the density of 100% Light Black
3. Measure the density of the next darker patch – 45% Black: Density
1.33.
Then it’s bit of simple math to calculate the percentage of black needed to
produce the same density as 100% Light Black. In this case we get a value
of 43.2% Black is equivalent to 100% Light Black.
I'm apparently math impaired because for the life of me I can't figure out a formula that will give me the answer of 43.2%Black. I can come close (43%) by trial and error but I think a formula would be better and in my case more accurate.
So, I guess my question is: can any one provide the formula for determining that 43.2% result.
Thanks