We consider capillary condensation transitions occurring in open slits of width
L
and finite height
H
immersed in a reservoir of vapor. In this case the pressure at which condensation occurs is closer to saturation compared to that occurring in an infinite slit (
H
=
∞
) due to the presence of two menisci that are pinned near the open ends. Using macroscopic arguments, we derive a modified Kelvin equation for the pressure
p
c
c
(
L
;
H
)
at which condensation occurs and show that the two menisci are characterized by an edge contact angle
θ
e
that is always larger than the equilibrium contact angle
θ
, only equal to it in the limit of macroscopic
H
. For walls that are completely wet (
θ
=
0
) the edge contact angle depends only on the aspect ratio of the capillary and is well described by
θ
e
≈
√
π
L
/
2
H
for large
H
. Similar results apply for condensation in cylindrical pores of finite length. We test these predictions against numerical results obtained using a microscopic density-functional model where the presence of an edge contact angle characterizing the shape of the menisci is clearly visible from the density profiles. Below the wetting temperature
T
w
we find very good agreement for slit pores of widths of just a few tens of molecular diameters, while above
T
w
the modified Kelvin equation only becomes accurate for much larger systems.