Sound a lot like the standard EV index that I use mentally, regularly. And for those who wish to use it, there are a couple of \'keys\' you can use to get there quick so you don\'t need to memorize the whole thing. F/5.6 equals 5. 1/60 equals 6. 1/1000 equals 10. If you need the aperture for an AV of 7, open up two stops from 5 (5.6 to f/11). If you need to figure the TV of 4, then decrease the shutter speed by two increments from 6 (1/60 to 1/15). Assuming ISO/ASA 100, of course.