The calculation isn't particularly elaborate. Use the lens makers equation 1/v + 1/u = 1/f, and calculate v and u to put in it from Canon's specs: v+u=3300mm (the mfd), and v/u = 0.2 (the magnification). You can't calculate the focal length of the zoom by relative magnification with primes because primes also focus breathe, which is why you are out by about 50%
Good info to have and clearly the most accurate. My two fingered approach is still useful in that it gives me an idea of what to expect relative to my primes. OTOH, as I said before, seeing is believing.
Generally I HAVE TO listen to Bryan(who is a friend) first and then Dustin Abbott. Bryan gives the clear technical advice, and Dustin talks about using it in the field compared to other lenses he has reviewed. I don’t pay much attention to others.
I would advise against giving two fingers to a Brit as you might not get what you expect.
Ah, yes, "two great countries separated by a common language". It does appear that it is important to note which way the palm is facing.
Sometimes there is a bit more subtlety to British language than there is to American language.
