Damien Parker, a friend of mine from Australia, asked me about faking Neutral Density Filters in post processing. At the time I was kind of stumped, but gave him a quick answer, “Try using masks and Gaussian Blur in PS”. However, his question planted the seed in my brain, and I was hooked on finding a better response.
After fiddling with the image from Concert #13 the Clarity slider in Adobe Camera Raw, I noticed the water started to blur in an unusual way. It started to blur, but keep some detail in a fuzzy way while keeping some very nice reflections. It was a very similar effect received from an ND filter.
I put that in the back of my mind until I tried it on a few more images. I kept opening them as smart objects and making history states and jumping through all kinds of hoops until I stumbled upon creating multiple Adjustment Brush points set to effect the clarity only. There it was, the faking of the neutral density filter!
video was cut off
That is odd. You may want to give it another go. I just watched it all the way through. Maybe trying going to YouTube directly.