I still have and use a wide range of F3 screens including the H series. Way back in the old pre-AF days these were the trade secret to shooting low-light sports with long lenses; the H series gets a radical 'shimmer' when out of focus and a clean 'snap' when in focus which made tracking a running back or forward with a 300 or 400 2.8 much easier. Many of my fellow news photojournalists were complimentary to my skills when they saw the next sports page. I just never told them or let them see thru my sports body set up HA!