San Francisco-based Breakthrough Photography has announced the first third-party drop-in filters for Canon's EF-RF drop-in filter mount. This filter mount allows users to adapt EF or EF-S lenses to EOS R series mirrorless cameras with a dedicated space for A-type drop-in filters.

Since the EF-EOS R drop-in filter mount adapter first launched, users have been limited to Canon's own circular polarizing (CPL) filter or variable neutral density (ND) filter. With Breakthrough Photography's new line of compatible drop-in filters, users will have access to more than 20 different X2 and X4 filters.

Breakthrough Photography's new drop-in filter line. Image credit: Breakthrough Photography

The design of Breakthrough Photography's new drop-in filters includes a rubberized grip to make it easier to put the filter in and remove it from the adapter. For filters with adjustment, there is a large ridged adjustment wheel. Each drop-in filter is also color-coded to make filters identifiable with a quick glance, which will be particularly useful for photographers who purchase one of Breakthrough's available filter kits, such as the Essential X2, Essential X4 or Complete B&W filter kits.

The Breakthrough drop-in filters include a large adjustment wheel and a rubberized grip. The filters are also clearly labeled and color-coded. Image credit: Breakthrough Photography

Before delving into specific available filters, let's consider the difference between Breakthrough's X2 and X4 filters. Looking at the X2 CPL versus the X4 CPL, the latter filter has an average light transmission of 50.64% whereas the former has an average light transmission of 42.44%. According to Breakthrough Photography, the X4 CPL 'moderately outperforms' the Canon drop-in CPL filter, whereas the X2 CPL has 'slightly less' light transmission than the Canon filter. In terms of color cast, the X4 CPL 'moderately outperforms' the Canon filter.

Breakthrough states that their X4 CPL filter has the best light transmission among its competitors. We can also see here that the Canon drop-in CPL filter performs well, as does Breakthrough's more affordable X2 CPL filter. Image credit: Breakthrough Photography

The X2 ND filters and X4 ND filters don't have a direct Canon competitor because Canon offers a variable ND filter rather than a series of solid drop-in ND filters. With that said, Breakthrough Photography claims that the X4 ND outperforms 'industry-leading manufacturers such as Singh-Ray and B+W and Lee' due in part to neutral color transmission.

Image credit: Breakthrough Photography

Canon's EF-EOS R drop-in filter mount includes a 1.5-9 stop variable ND filter. In addition to solid ND filters in 3, 6, 10, 15 and 20 stop strengths, Breakthrough's new drop-in filter line includes a pair of variable ND filters. The first, VND-R, is adjustable from 2 to 11 stops. There is also a stronger Dark VND-R, allowing adjustment from 10 to 16 stops of ND strength. Breakthrough states that the VND-R and Dark VND-R drop-in filters eliminate the 'X' pattern sometimes seen on VND filters with wide-angle lenses. The Canon drop-in VND is an excellent filter but Breakthrough states that their filters outperform it. You can view a transmission percentage comparison below.

There are four CPL filters in the line aimed at black and white photography: Red, orange, yellow and green. They are available in a bundled set.

Comparing Breakthrough's available black and white CPL filters. Image credit: Breakthrough Photography

Rounding out the series of drop-in filters are Night Sky, infrared 720nm and a pair of clear filters. Digital cameras, such as the EOS R, RP, R5 and R6, include a permanent IR-cut filter over the image sensor. With the IR filter, some residual light can reach the sensor and show the scene in a way different from how it appears in the visible light spectrum. The Night Sky filter is designed to reduce light pollution and show night scenes with color neutrality.

Breakthrough's Night Sky filter aims to reduce the impact of light pollution on colors in night sky images. The image on the left was captured without the Night Sky filter, whereas the image on the right was shot using the Night Sky filter. Image credit: Breakthrough Photography

Breakthrough Photography expects the filters to begin shipping in late September. Prospective customers can preorder individual filters and filter kits now through Breakthrough Photography's website. Prices range from $80 to $200 for individual filters. There are also savings available if customers opt for a filter kit rather than purchasing a set of individual filters. It's worth noting that all Breakthrough Photography filters include a free 25-year 'Ironclad Guarantee'. If you'd like to learn more about long exposure photography while you wait for your new filters to arrive, Breakthrough Photography offers a free 52-page long exposure photography guide, which you can learn more about here.