I love working with PSE8, yet it doesn't do everything that I would want it to do. Having a physical ND filter or a Grad ND filter on the camera as you take your picture can do things that utilizing a ND filter function on PSE8 cannot do.
With these two shots, I wanted to bring out the intensity of the sky and bring some definition into the clouds.
The unmodified image of a DH-8 coming into land on Runway 26R
When I applied the post-processing ND 1.2 (4 stop) filter simulated by PSE8, the sky was darkened and the clouds gained definition.
This shot, I underexposed a bit to bring out the clouds, however, that was not bringing out the clouds in a way that I wanted.
With this shot here, I cranked up the exposure of the RAW file by one stop, then applied a 1.2 soft ND Grad with PSE8 (post processing) to the photo with the transition point to the center-line of the aircraft. This allowed a gradual transition from the clouds to being able to see the aircraft. The clouds are being lit by the setting sun and that was the intensity that I wanted to bring to them. The problematic part of throwing a GND or ND filter PP on the aircraft is that you are going to end up with a dark aircraft. You can either use shadows to tweak the exposure, or you can dodge (using the dodge and burn tool) as I have in this updated photo. Learning how to utilize the "dodge and burn" tool is essential in post-processing and if done right, it can make a world of difference in your photos.
The dodging and burning allows you to bring out the exposure of the aircraft and ONLY the aircraft, not the darkened sky behind it.