[old_tv_nut]

By the way, when you say "aperture 3.5" and "f/16" these are contradictory. The 3.5, I suspect, is the maximum aperture of your lens, but you are really stopping it down to f/16.

The best resolution of many lenses is around f/8 or so, but any aperture from f/4 to f/16 is probably good enough to resolve the phosphor dots.

Since you seem to be keeping a shutter of 1/30 second while varying aperture, your camera must be automatically adjusting ISO. Using f/16 may be forcing the ISO higher than necessary, so I woud try f/8.

Your camera seems to be doing a good job, but you might try full manual mode: Set ISO at perhaps 400 for starters; set shutter at 1/30; then see what aperture gives a good exposure. If you can't get a reasonable aperture with ISO 400 and 1/30 second, adjust the ISO to allow a reasonable aperture. The goal is to not use an unnecessarily high ISO, which introduces noise.