I know that selenium ones, the no batteries needed type, do. What about CdS? I build a Knight LG-275 light meter when I was a freshman in college, 1965, probably. That new CdS technology was all the rage! That particular meter got lost along the way, so I found another one on eBay for nostalgia purposes. And I still have the user manual! The two 1.35v PX625 mercury cells are of course, history. So the local electronics shop ordered me two of the 1.5v alkaline ones. In typical EV 15 outdoor bright light, the meter would swing past full scale. Man, that's only .3v or 11% more voltage. I'll bet that the meter would still be happy with 2.4V, the same amount off but less instead of more. Being incredibly clever, I figured that all I needed to do was adjust the potentiometer on the back of the meter for a full scale battery check reading, and it's me and Ansel, right? Wrong. However, I did get EV 15 reading with micro-fine twiddling with the pot (and lots of sweat, standing in that late PM Florida sun.) My Vivitar 45 match needle meter also used mercury cells. Now with alkalines, the meter swings only a bit more, nothing like the overread of the Knight. It's spot on if I use the left side of the target circle instead of the middle. My Knight now agrees with it under various lighting situations. My cheapo Tundra meter uses a silver oxide battery, so I do have a confirmation of EV 15 out in the bright light. Soooooo, it would appear to me that the CdS cell has lowered its internal resistance quite a bit for a give luminance level. All this also raised the ugly fact that the new batteries, of course, don't work right in my cameras. (The last time I was using them much I still had mercs in them.) They are off by a full stop, needing to be set at 200 for 100 film. What's really aggrevating, as any electrical geek knows, all any of these folks had to do was use a simple bridge circuit instead of the voltage reference of the battery, no problemo.