2. Specifications of Photocells (LDR)

In the past photoresistors (LDR, photo cells) were very popular
as ambient light sensors because their spectral sensitivity
matches the V(λ)-curve quite well and the price is low. The
disadvantages of the photoresistors are the wide spread and the
memory effect of resistance values. The main problem, however,
is that photoresistors contain Cadmium which is banned by
RoHS. Thus LDRs can only be used in applications which are not
covered by RoHS.