Hoya vs Tiffen Variable ND filters?

In general, most photographers stay away from the variable NDs because on wide angle lenses you get a cross polarization effect that results in an X like pattern of polarization.  This is due to the way they are constructed which basically is a sandwich of two polarizing filters.  You tend to not see it at 50mm or above but the wider you go the worse it gets.  In general if you have a polarizer and then get a 5 or 6 stop filter and a 10 stop filter you will be all set for any situation.

I tried one a few years ago on a 28mm and found exactly what E.J. said. It was unusable in my opinion. I returned it.

Thanks, sounded too good to be true. I have several straight ND filters. I was just trying to get rid of some of the "clutter."



body{zoom:125%!important;}

I had seen EJ's answer before, so I also have only  ever used straight ND filters and/or a polarizer.

On the subject of reducing clutter, though, I do 2 things:
1. I only buy 77mm diameter filters (the largest filter ring diameter of my lenses) and use step-up (down?) rings for the smaller lens diameters.  It avoids having several sets of filters, at the cost of a few adapter rings.
2. I stack all the filters together and use protective metal stack caps on the ends of the stack.  In case you aren't sure what I'm referring to, search Amazon for "filter stack caps".  Of course if you have any ultra-thin filters (which often don't have a front thread) for wide angle lenses, this won't work for them.