Aurora PowerND CR Rear Mount ND Filters for Canon EF Lens (3/6/12/16 Stop)

Description

Aurora CR Format ND Filter Set
Rear Mount Glass ND Filters for Selective Canon EF Lenses
As part of our PowerND product family, the Aurora CR filter set comes with a CR filter holder and four CR format ND filters in the rating of ND 8 (3 stops), ND64 (6 stops), ND 4000 (12 stops), and ND 65000 (16 stops).
We take advantage of some Canon wide-angle lenses having a rear mount filter holder for gel filters and have designed a replacement of filter holder for glass filters.
The CR filter holders are CNC machined with utmost precision. Not only it allows the Aurora CR format glass filters to be used, but they are also much stronger than the original factory built in plastic holding mechanism.
The reason of using the rear mount filter over the front one is primarily the size of filters. Based on our simulation, if we were to make a front mount filter for the Canon EF 11-24mm F4L USM, a lens that is very popular among the Canon landscape shooters, a front mount filter size would be at least 185mm or larger, either in circular or square format. Filters of such size are not only inconvenient to carry and use, but also very expensive.
Another reason for using our rear mount glass filters is that gel filters are optically inferior with significant resolution degradation and strong color cast. In order to achieve accurate color reproduction and high resolution, we apply multi-layer nano-coating to both sides of the PowerND 4000 and PowerND 65000 filters. The end result is that we achieve excellent result in resolution and color rendition.
One of the additional benefits of having a filter between a lens and a camera is zero vignetting and ghosting effects often seen in front mount filter.
The CR filters are coated with the same multi-layer nanocoatings for surface protection against water, oil, dust, and dirt. Perfluoropolyethers (PFPE) are used as a hydrophobic and oleophobic coating agent. With such a coating, we are able to achieve a static contact angle of 110 degrees with water droplets on the surface of the filter.
As avid landscape photographers ourselves, we understand these filters are used in a harsh environment, in places that could be rough, dirty, and wet. Therefore, filters should be able to repel water, oil, dust, and dirt.
Static contact angle of PowerND coating
Multiple layers of nano-coating technology are applied to glass surfaces. Perfluoropolyethers (PFPE) are used as a hydrophobic and oleophobic coating agent. The end result is that water droplets on the surface of the filter can maintain a static contact angle of 110 degrees. Untreated glass can barely maintain 15 degrees. Even a well-known brand’s 10 stop filter keeps less than 40 degrees and their 6 and 15 stop filters do not even have water repel coatings.
Static contact angle of Brand L (no coating)
Gorilla Glass® is used for the CR filters to provide rigidity and durability for such small size filter. It’s the same type of glass used in modern smartphone screens.
Canon lenses compatible with the CR filters include:
EF 8-15mm f/4L Fisheye
EF 11-24mm F4L USM
EF 14mm f/2.8L USM & EF 14mm f/2.8L USM II
EF 15mm f/2.8 Fisheye
EF 16-35mm f/2.8L USM (EF 16-35mm f/2.8L II USM not supported)
EF 17-35mm f/2.8L USM
EF 17-40mm f/4L USM
Left: Aurora CR filter, Right: 186mm front mount filter
CR format PowerND 8 (ND 0.9) – 3 stops
CR format PowerND 64 (ND 1.8) – 6 stops
CR format PowerND 4000 (ND 3.6) – 12 stops
CR format PowerND 65000 (ND 4.8) – 16 stops
CR filter replacement adapter
Screwdriver
CR Adapter Installation Guide
Additional CR filter replacement adapter is also sold independently.
Shipment
International buyers are responsible for any import duties and customs clearance in their countries.
Items will be shipped from Hong Kong.
Warranty
Products are free of defects in material and workmanship for a period of three (3) years from the date of purchase.