  Bj\"ork, Jonsson, and S\'anchez-Soto describe an interesting
(gedanken-)experiment which demonstrates that single photons can indeed lead to
effects which have no local realistic description. %It is one of few cases
where the experimental falsification of the conjecture of local realism has
been done with use of the CH inequality, rather that the CHSH inequality. We
study the critical values of parameters of some possible features of a
non-perfect realisation of the experiment (especially photon loss, which could
be looked at as the detection efficiency), that need to be satisfied so that
the experiment can be considered as a valid test of quantum mechanics versus
local realism. Interestingly, the scheme turns out to be robust against photon
loss.
