This rather complex formula shows you how to solve this puzzle using accepted scientific methods.
The calculations to be performed on the measurements taken depend on the technology used, since beta counters measure the sample's radioactivity, whereas accelerator mass spectrometers (AMS) determine the ratio of the three different carbon isotopes in the sample.
The fossil fuel effect was eliminated from the standard value by measuring wood from 1890, and using the radioactive decay equations to determine what the activity would have been at the year of growth.
Because of the fossil fuel effect, this is not actually the activity level of wood from 1950; the activity would have been somewhat lower.Since it was created after the start of atomic testing, it incorporates bomb carbon, so measured activity is higher than the desired standard.This is addressed by defining the standard to be 0.95 times the activity of HOx I.All of this first standard has long since been consumed, and later standards have been created, each of which has a given ratio to the desired standard activity.
Another standard is the use of 1950 as "present", in the sense that a calculation that shows that a sample's likely age is 500 years "before present" means that it is likely to have come from about the year 1450.
This convention is necessary in order to keep published radiocarbon results comparable to each other; without this convention, a given radiocarbon result would be of no use unless the year it was measured was also known—an age of 500 years published in 2010 would indicate a likely sample date of 1510, for example.