Quote Originally Posted by Roger Cole View Post
You're right. My mistake.

I should have said is that CdS cells are much less linear in their response WRT intensity, making meter design more difficult.
Selenium, or more properly iron selenide, cells are photovoltaic cells. They actually generate an EMF when light falls on them. All the other 'cells' you mention are photoresistive, that is the rseistance changes according to the intensity of illumination.
The Gossen LunaPro (LunaSix, LunaSix 3) was indeed a CDS meter, and the battery problem isn't a problem if you use #675 hearing aid cells with 3 of the 4 airholes blocked for longer life (up to a year).