Getting old and finding it a bit harder to manually focus any of my DSLR's. The existing viewfinder set-up and screen isn't really expecting you to do much manual focusing - I miss the old split circle set-up on my film cameras. Not a huge issue but I clearly could use some help on real 'reach' shots when using a TC and I can't rely on AF to work..... say the 1.7 or even 2.0 with the 200-400. KatzEye focusing screens look like a solution. http://www.katzeyeoptics.com/page--K...lus--plus.html Anyone tried these? Installed them or had them installed? Comments, suggestions, recommendations, warnings? My wife also misses grid lines on her D40 - this looks like a way to take care of that too.