Apeture Calculation

Quick question - My strobe table gives me distances v.s. apeture settings. Are these distances calcualted from the front of the lens, or from the film plane. I have just bought a Kenko 2x teleconverter which makes me loose 2 stops, and I am trying to figure out what the apertures will be at max focus appeture settings for the Nikon 60mm and 105 mm for 2:1 macro using YS - 90 strobes ( 2x )

In my Ys-25's manual its writing that the distances is from the strobe and not from the lens.

Thanks,

I think that is what is says, but for example, if I have the strobes on long arms which are 10cm from the subject, but am 30 cm with the lens from it, there will be light fall off over the 30 cm's . ( theoretical example )/

Lucky we use digital, so we can test & fix in real time.

I wrote on my slide a table with a startup values for object in few distances (e.g. distance: 1/5 m, F=8, Flash = 4)

I Check the result of the first shots every dive and fix the values to the current dive if needed.