Ideally, a hydrogen fuel-cell vehicle has no environmental impact. Energy is produced by combining hydrogen with oxygen pulled from the atmosphere, and the tailpipe emission is water. The hydrogen fuel could come from a number of sources (Iceland recently started pulling it out of the ground).
4) Fast, Slow and Long Shutter Speeds. Fast shutter speed is typically whatever it takes to freeze action. For me, it is typically above 1/500th of a second for general photography and above 1/1000th of a second for bird photography. NIKON D700 @ 420mm, ISO 450, 1/2000, f/5.6.
Mode (Tv). In this AE mode you set the shutter speed (time) by rotating the main dial located next to the shutter release button. The camera will then automatically set an appropriate lens aperture for you. Tv stands for âTime value.â Use this mode if specifying the shutter speed is important. For example, you may want a fast shutter speed to freeze motion or a slow shutter speed to blur it.