Let $E$ and $F$ be Banach spaces. Let $f(t)$ be a measurable map takes value in the space of bounded linear operator from $E$ to $F$, i.e. $f(t)\in L(E,F)$ for any $t\in Dom(f)\subset E$.
Now, I see that the range of $f(t)$ is the set of all elements in $L(E,F)$. This implies $f(t)$ may takes value in $F$? What is the domain of $f(t)$? $E$?