I have a whole box of older filters, variable, fixed, CPL, etc. Over the last year I discovered a new breed of ND and CPL filter from a company called Breakthrough Photography. These filters are really transparent and the best I have ever used, by far.
Their rings are made of brass, with a tread on the outside that makes the ring easy to grip. The brass rings are electroplated in matte black, engraved with laser-etched filter type and even a serial number
The glass is made from Schott B270 ultra-wide glass. The glass then has a hydrophobic nano-coating (beads up with water), eight layers deep on each side, which means 16 layers of coating. The 16-layer coating is harder than the filter glass and even resists fingerprints.
As for color tinting, there is little to none, no significant color cast, remarkable compared to all my older ones.
Each filter comes in a solid plastic box, with opposing finger holes to grab and replace the filter, a big help.
They come with exquisite packaging, not that that is important to me, and even include a micro-fiber cloth with each filter.
I have their 3-stop and 6-stop X4 Neutral Density filter in the 77mm size. I also have their X4 CPL (Circular Polarizer) in both 77mm and 95mm size.
In addition, they make a superb Universal Arca Plate in the business for $12 and the very best step-up rings I have found, built with the same quality and craftsmanship as their ND filters.
Here is my setup:
I have a lot lenses, so I settled on the main filter sizes that I most use, which are 52mm, 58mm, and 62mm. I purchased step-up rings for each of these filter sizes to fit 77mm, so I have 52mm-77mm. 58mm-77mm, and 62mm-77mm, all using the BreakthroughPhotography step-up rings.
That way I can use 77MM filters for those sizes and for my 77mm lenses. In addition I have a step-up ring from 77mm to 95mm, in case I want to use the larger 95mm filters on the smaller lenses.
If you want to read more, here is a link:
http://breakthrough.photography/One More Thing:
To make things even easier I use XUME magnetic adapters on all my filters (or most of them). What XUME adapters do is allow me to snap-on filters to all of these lenses. I install an XUME lens ring on each step-up ring (three in all for my work). And I put a magnetic matching ring on each ND and CPL filter.
When I shoot, I take with me the step-up ring with the XUME lens ring attached. I screw this into the lens I am using. Then I can just slap on a CPL or various ND filter as needed in a flash, and take it off just as easily.
This really works out well in cases where otherwise I might be too lazy to go through the trouble to screw in all the filters, etc.
If you want to read more, here is a link:
http://www.xumeadapters.com/Photograph of the Breakthrough ND filter, and the second image is the XUME lens ring and matching magnetic filter ring.