It's not a meter pe se, but it's a flash calculator and a step-above the simple cardboard wheels, so I thought I'd add it here. It's the sister to the Norwood Director Speedrite, which was designed to be used with electronic flash (aka speedlites). This one is meant for bulbs.

I hate bulbs. A lot of people (including me) are nostalgic for various things, but very few people miss flash-bulbs. They were slow, they were often awkward, they didn't always go off, they were finger-burning hot when they did, they broke if you dropped them, and in general were a pain in the ass. Plus there were a multitude of different kinds. Nothing was straightforward where bulbs were concerned. Speedlites were sooooo much nicer.

Both the Flashrite and Speedrites work on the novel idea of incorporating an actual rangefinder tool with a calculator. When you have to manually set up a flash, you need to know the camera sync speed, the guide number for your flash, and the distance between your flash and the subject. If you know those, you can compute the f/stop for your lens. Since most cameras at this time (early 50s) didn't have rangefinders, this tool made it a little easier to figure it out.

The key word there is little. To use this thing you had to find the bulb you were using on the outer edge of the dial, and trace the curving tail down to the intersection between the shutter-sync speed orbit and the film-speed radial. Got that? Then you look through the range-finder and merge the images. Then it will tell you the f/stop to use.

I can see my uncle Doug, an engineer and hobbyist photographer, using this thing, but not my aunt. But then, Doug probably could have done the guide number math in his head faster than he could have set the calculator.

This was also sold by another company as the Flash-Mate. I suspect that Director Products dropped it and the other company bought the unsold inventory, but that's just speculation.

A similar (albiet better) meter is the Tower Flashometer. It's much easier to use and more compact.