  Motivated by the recent work about the Extended Uncertainty Principle (EUP)
black holes \cite{Mureika:2018gxl}, we present in this study its extension
called the Generalized Extended Uncertainty Principle (GEUP) black holes. In
particular, we investigated the GEUP effects on astrophysical and micro-black
holes. First, we derive the expression for the shadow radius to investigate its
behavior as perceived by a static observer located near and far from the black
hole. Constraints to the large fundamental length scale $L*$ up to $2\sigma$
level were also found using the EHT data: for Sgr. A*, $L* =
5.716\text{x}10^{10}$ m, while for M87*, $L* = 3.264\text{x}10^{13}$ m. Under
the GEUP effect, the value of the shadow radius behaves the same way as the
Schwarzschild case due to a static observer, and the effect only emerges if the
mass of the black hole $M$ is around the order of magnitude of $L_*$ (or
$l_\text{Pl}$). In addition, the GEUP effect increases the shadow radius for
astrophysical black holes, but the reverse happens for micro-black holes. We
also explored GEUP effects to the weak and strong deflection angles as an
alternative analysis. For both realms, a time-like particle gives a higher
value for the weak deflection angle. Similar to the shadow, the deviation is
seen when the values of $L_*$ and $M$ are close. The strong deflection angle
gives more sensitivity to GEUP deviation at smaller masses in the astrophysical
scenario. However, the weak deflection angle is a better probe in the micro
world.
