free variable

The Canon Canonet GIII QL17 is a classic rangefinder from 1972. It was designed to use mercury batteries that are now unavailable in the U.S.¹; substituting contemporary batteries results in metering errors that change over the life of the battery, according to Wikipedia:

The lightmeter uses a PX625 mercury battery, which is now discontinued. The alkaline version can be used, but the different electric tension, different discharge curve, and absence of electronic compensation circuit, induce a defective exposure metering, between a 1.5-f-stop at the beginning of the life of the alkaline battery, and a 1.5-f-stop underexposure [at] the end.

At first glance, it seems absurd, or at least quaint, that someone would put up with inconsistent exposures and the absence of modern amenities in order to use this camera in 2008. (And people do make a lot of nice pictures with the Canonet even today.) However, when one considers all of the crap that people have to put up with to use a 2007-vintage, $10k Leica M8 digital rangefinder, worrying about a stop or two here and there suddenly doesn’t seem like that big a deal.

¹ This decades-old restriction on mercury batteries looks awfully prescient now, since we’ll need to ensure a ready supply of mercury for light bulbs in the next decade. Good show, lawmakers!