>>4026217Ballpark is half-stop, or a difference of 25% transmission.
Super overkill answer is that there's a few factors that make it impossible to say without finding the actual light transmission of the specific lenses.
t/stops measure actual light transmission. f/stops are just math.
There's also the possibility of rounding (is that f1.7 closer to f1.70 or f1.74, etc).
In some cases, like with STF / APD lenses, the light transmission is significantly less. The Fuji 56 f/1.2 APD wide open is closer to t/1.7.
