While working in Rockford Il., I had the chance to go capture some amazing clouds and flowers in the countryside. This image is a composite of two setup to imitate a Graduated Neutral Density Filter.
The master of the Graduated Neutral Density (or GND) filter was Gallen Rowell and most are understudies of his work:-) The idea is that the sky is typically MUCH brighter than the foreground and this becomes very true at times like sunset. Digital, being like shooting chrome slide film, does not respond to light like the eye does. The eye can see a brightness of somewhere between 10,000 : 1 and 1,000,000 : 1. Digital and slide film, however, are at best 2,000 : 1 and 300 : 1 is more typical. This is why when you take a beautiful picture of a sunset, all you get is a silhouette OR a bretty foreground with a white sky. There is simply too much light in the sky and not in the foreground.
The point of the GND is to help balance out the scene by providing different exposures to the top half VS the bottom half of the image. By making a filter that is clear on the bottom and dark on the top, it is possible to take longer exposures to exposure the foreground while not making the sky white. With digital, you take two exposures and blend them in your favorite editing program: