Quote Originally Posted by GlennSYD
I use a 1.5v battery and have had no issues with metering, although I usually run only B&W film through it. The meter compares within 1/2 stop of a friends Leica M6 so it's close enough for me.
I can give you some real-world feedback. I use that "wrong" battery in my GIII and have no trouble with it, if you are of the mindset that the meter is offering a suggestion on exposure and not a mandate.

In my highly-accurate laboratory grade test light box (the blank bathroom wall with the lights on dimmer) the QL17 GIII agrees exactly with the lab standard (a Pentax K1000 which consistently gives good exposures).

In outside sunny-16 conditions, the GIII inidcates a slight overexposure, maybe 1/2 stop, compared to the Pentax.

I consider both of these tests to be well within the ballpark, and the real-world test, shooting slides, confirms it. On a recent roll of Kodachrome 64 I bracketed a few shots I wanted to be sure I got right, and the middle ones were consistently the best exposed. This is my experience on this subject anyway.