The numbers on the scale represent adjustments to the f-stop, either wider open than normal (smaller number), or close down the iris (higher number). The higher the number the deeper your “apparent” depth-of-field. The actual plane-of-focus remains a definitive distance from the lens but the higher the f-stop (the more closed the iris) the more of your subject appears to be in acceptable focus both in front of the actual plane-of-focus and also behind the plane-if-focus. F18 is a very closed-down iris and offers more DOF than you would normally need. You choose an f-stop that gives you adequate DOF for the situation but still gives you a fast enough shutter speed. With “OS” on-board you would still quite possible need at least 1/400 sec to get the subject sharp (once focused correctly) without camera wiggle blur. I need to shoot much faster than that, even at only 200mm, because I have no lens stabilization.
Your auto lighting optimizer is not set at maximum. Icon on the screen on the right side at middle height. You do not display all three vertical bars on maximum. Not a big deal.
OK, sure, helping someone is fun, but not as much fun as having a 600mm lens. What can I say, I’m self-absorbed. At this stage of the game, even if I had a 500mm lens I couldn’t do anything with it except stroke it with puerile affection. There, there …. nice lens.
