Just got my Heliopan Vari ND today, so I took a couple quick shots outside on a cloudy afternoon to see how it performs. Gotta say, it's incredible using a filter like this when you've used cheap $10 vari ND's for so long. No color cast, no loss in sharpness... it's definitely something I should have invested in sooner.
Later this week I'll be putting up a side by side comparison with the Neewer and the Heliopan, so you can get an idea of what the difference is between the cheapest and best Vari ND that you can currently buy!
I'm constantly slapping on filmconvert to most of my videos now... ha, gotta stop doin that for EVERYTHING... but it's too damn addictive.