The Tiffen "Variable" ND filter
I went and bought a 77mm Tiffen "Variable" ND filter (often referred to as a "Fader"). This is one of the highly recommended inventions for this year, allowing you to get great sky shots with your high-end SONY lenses, which are all basically fitted with a 77mm filter ring.
The beauty of this thing is that it will give you an additional 2-8 stops of light reduction (0.6-2.4). Simply twisting the filter ring and much like the polarizing filter... the light is effectively reduced and controlled, before it ever gets in the lens or the camera.
If you do not understand what a Neutral Density filter can do for your photography, you really need to check it out. ND filters are one of the best methods of deal with sky, motion and DOF issues. Many people use "graduated" NDs, which are a good choice, but require attaching the filter, aligning it with the horizon, taking the shot and then its subsequent removal. This "variable" ND could be on the camera when you start your outdoor shoot and with a quick twist, you get your well-timed shot with 2-8 tops of light control, aside from you aperture setting.
As we all know, changing the aperture alters the Depth of Field (DOF)... the ND filter reduces light without changing the DOF. Also, a tighter aperture (above f/13) causes the image to involuntarily soften on a digital camera due to diffraction. The addition of a ND-filter allows you to back off the tight aperture and still get your image. Like they say: "An effective f/8 and you look great!"
I went with the 77mm size for SONY's commonality among the high-end lenses, but you can get a set of filter-ring reducers and use it on many other lenses, too.
Anyway, more on this... later, when I get the darn thing.