Okay, now we're talking about the shutter priority creative zone mode on the Canon 40D. In order to set your camera into shutter priority mode, you need to turn the dial on the top side of your camera on the left side, when you're facing the camera from the back. It is indicated with a upper case T, lower case v, so there my camera is lined up with the white line on the body, with the Tv on the mode dial. So I'm now in a shutter priority mode. What I can do now is manually set and control the shutter setting, but the aperture will automatically be set to compensate for my shutter setting. If I hold down the shutter button, I can use the main control dial to increase or decrease my shutter settings. So right now I'm increasing it, and I can go all the way to 1/4000th of a second. Now you can see right now my aperture is blinking, which means that, that's going to be not enough light. Even at the whitest aperture 1/4000th of a second is really, really, fast so I need to scroll back down here to find a shutter speed that will work. Now the aperture stops blinking at 1/1250th of a second, and it looks like that will give me an appropriate exposure. If I wanted to scroll back down the other way, toward bold setting, I can go so far as to, let's see here, looks like thirty seconds. Thirty seconds is the longest shutter speed I can manually program without putting the camera into a bold mode. But you can see again that the aperture is blinking on the camera, letting me know that the exposure with thirty seconds will be way too much. The picture in this case, is just going to be totally blown out, there's too much light. So I'm going to scroll back the other way, slow it down, let's speed up the shutter speed here a little bit until two seconds, two and a half seconds, and it looks like at the smallest aperture, two and a half seconds will give me an appropriate exposure. So again, shutter priority mode is mainly to give you control over the sharpness of your picture, a faster shutter speed will give you a sharper image, a slower shutter speed will give you the sense of movement a sense of action. So, take some time to mess around with it, get some experience and be creative.