It will be in a different spot depending on what the dominant wavelength is (i.e. what filter you put in front of what film) you want to record.
This is a tricky one.
You need to know how the particular lens performs in that range to be able to give an answer. Or put in other words: you do have to know the answer to know the answer.
Not something you can calculate based on 'trivial' data like focal length.