I know a number of light meters that are built into film cameras.
First, there are selenium light scopes, as on the lower old Canonet.
Later, cadmium sulfide (CdS) photocells became more abundant. This later Canonet model used one. It is located directly above the front element of the lens.
Thereafter, silicon photocells have become the norm, with increasingly complex segmented meters with transmitted light measurement offering options such as center-weighted averaging, sub-metering, spot metering, and evaluative (Canon) or matrix metering (Nikon).
What other built-in counters used film cameras in addition to the above meter types (selenium cell, CdS cell, TTL silicon multi-segment)? Is there a complete list of useful categories?
(all images courtesy of Wikimedia Commons)