Following the comment of PH Photography on the quality of the Fader ND, I decided to do more extensive testing. As I was stating in my original review, I was having great results while using the Fader ND in video mode with my 24-70 (main video lens).
So, today, I decided to review what I have shot so far in Iceland with the filter. Up until this morning, everything was shot with the 17-40L4 and was good enough to be put on the web at 720p. So I was having different results than what PH Photography was getting. Then, I reviewed the clips shot with the filter mounted on my 400L5.6. Oh boy!
These clips are not sharp at all. While very usable for web display in a downscaled window (as on Vimeo), the 100% crop was not satisfying at all.
I understand that using a variable filter at such a long focal range is not common so this might be the reason why so few people have reported the issue. That being said, I am getting very good results with my other lenses. If someone has a 400mm lens and a Sihn Ray, I would love to hear your results.
Now that I think about it, anyone else experienced sharpness issues with the Fader ND on a telephoto lens?
Should you forget about the Fader ND?
Fortunately, the Fader ND manufacturer is coming very soon with a revised version of the product which will be using much higher quality glass. Cant wait to test these out. Until then, I will not use the filter on any of my long focals.