Heaton discusses his decision to go with the f/4 version of this lens over the f/2.8. As he doesn't do astrophotography, he chose to purchase the f/4 for the cost savings. Most landscape images aren't shot wide open (f/8 or f/11 being a more common aperture to ensure sharpness throughout the image) so it makes sense to get the f/4 and save some money.
Heaton envisions using his new ultra-wide-angle lens not necessarily to capture wide vistas, but to create compositions with interesting foreground elements, emphasizing those elements and stretching them into the distance by placing the camera closer to the ground. To demonstrate, he takes us to a beautiful, moody beach location on the northeast coast of England.
With the aid of a Lee polarizer to remove glare on the rocks and water, a 2-stop ND filter to avoid overexposing the sky, and wide-angle filter adapter (used so that the filters sit closer to the lens for reduced vignetting), Heaton takes us through the set up and capture stages of the image.
One note: placing the wide-angle lens right in front of an object for exaggerated interest will not result in a sharp image from foreground through background. Heaton solves this problem by focus stacking three separate exposures (focusing on foreground, midground, and background, respectively in each) and blending them together in post.