Before digital imaging came about, a lot of the lenses produced had a rear gelatin filter holder. Rosco & Lee make gels in a wide range of colours and neutral density values. These gels come in a range of colours and ND values. CTO or CTB filters were commonly used to correct the white balance of the image. Now with digital imaging, it’s much easier to adjust the white balance in post.
Today, the mount is still used by many to add ND gels for long exposure photography. While it is a cheaper option to use ND gels instead of a front-mounted filter system, it does have its disadvantages such as causing ghosting or flares in the image.
Framing your subject is also an issue when using strong ND with an optical viewfinder as you need to remove the filter to see the frame and then place it back when taking the shot. With current cameras, using live view on an EVF or LCD, you can get around this issue to a certain degree.
Industry First Aurora CR format
Installing the Aurora CR format mount
Replacing the mount is easily done by removing three screws.
Once the new mount is installed, it can securely hold the glass filter in place.
You can see the massive difference in size between the Aurora CR format and a 186mm round filter.
Pricing & Availability
The Aurora CR format kit is available for purchase via authorised resellers for $269 USD
Aurora PowerND CR Rear Adaptor Filter Kit – $269 USD
Individual CR Rear Mount adaptor – $29 USD