ALPA HPF rings - first hand experience? - The GetDPI Photography ...
The problem has been that even though I can accurately estimate 12 feet, I don't have a good idea of where 12 feet is on the existing focus ring of the lens. Of course this will also work very well with a laser ranger but interestingly , I have found that even though many Alpa users have laser rangers, few of them use them much after one or two months. For example I can easily tell if something is closer to 12 feet away than 14 feet away.