At CP+2019, Canon was showing the Drop in Filter Mount Adapter EF-EOS R with the variable ND drop-in filter.
The new adaptor and variable ND drop-in filter has started shipping in Japan and will ship in the US soon.
From our hands-on test with the setup, we found that you could use it effectively to make slight adjustments to exposure while recording video.
The drop-in filter is handy to use especially with wide angle lenses which usually require large filters and adaptor rings.
The ND filter has a range of ND3 – ND500 which is equivalent to 1.5 – 9 f-stops. There is also a circular polarizer drop-in filter.
The EOS R Drop-in Filter Mount with Variable ND retails for USD $399.
The EOS R Drop-in Filter Mount with Circular Polarizer retails for USD $299.