#1. "RE: Error/Warning message - Not enough light on subject" In response to Reply # 0
Seattle, WA, US
You were giving too much control to the camera. For lightning shots you should be in manual mode as the camera is trying to get a correct (medium gray) exposure for the dark sky and knows nothing about the "never there" lightning.
30 sec at f/8 with ISO 100 is not a bad place to start, although f/11 or f/16 might be better.
---------+---------+---------+---------+---------+ Joseph K Seattle, WA, USA
#2. "RE: Error/Warning message - Not enough light on subject" In response to Reply # 0
For long exposures at or near the 30 sec. Limit of the cameras Auto Exposure capability you should use Manual Exposure mode. In addition Lightning has a short duration and the cameras meter will measure the ambient light level without the light from the lightning included in the exposure calculation. Therefore any images with lightning in it will more than likely be over exposed. Also at night the cameras meter will overexpose for ambient to start with assuming a dark scene providing an image that looks more like daylight than a night scene.