Harold Owen (Yahoo! FZ10 forum, 7 April 2004 and 9 April 2004)...
As an example if I have the FZ10 set on f5.6 and focal length is 6mm (35mm equivalent) I know from using the `hyperfocal caluculator' that I need to focus on an object at a point 4.1ft away, in order for the scene to be in focus from 2.05ft to infinity. I can set the `accessory rangefinder' at 4.1ft on the rangefinder scale and just look through it to find a point that is in focus, I then focus the FZ10 on that point.
Ideally the camera would be either in aperture priority mode or totally manual mode to make the process easier.
Using a 'hyperfocal' setting allows one to get grab shots in an instance.
It is really useful for taking landscape shots as one will know exactly the areas that are going to be in focus.
...accessory rangefinders can still be found at some camera shops in their second-hand section.
I have often wondered whether any manufacturer had introduced a modern rangefinder, I did read somewhere that there are rangefinders but they are for rifles I believe.