"green mode" is just a pre-set mode. You'd use green mode for the shots you do all the time. In theory, you get to pre-program in all the functions of the "green mode". Ie, ISO x, shutter speed y, flash on/off, etc, etc. Once programmed in, you don't get to change what Green Mode is.

Probably great if you constantly took one kind of shot all the time. But, seeing how the outdoors changes all the time, green mode probably isn't a good choice.

You want to be in the "P" or program mode. Or, unless you know the shooting situation you are in, you can use one of the other "modes" provided on the camera.

How many images you can store on a card depends on the image quality and compression level you set on the camera. The higher the quality level and the lower the compression level, the bigger the file will be, hence the lower number of images you can store on a card.

My rule of thumb is ALWAYS crank the quality to max, and the compression to zilcho. I want the most information available on an image, and I don't want any compression.

You'll kick yourself when you land that 30 pound steelhead and your camera is set to some wussy low-end resolution setting. So much for that wall hanging BIG print out.

Remember, you can always DOWNSIZE an image later. You can not UPSIZE a small image later. Always, always, always, save big images. Just use a photo program to crop them down later.

As I said, with the resolution cranked and the compression dropped, my camera says it can hold 330(ish) images on the 1GB card.

A 512 card should hold roughly half of that.

I'd crank up the resolution and drop the compression if I were you.....