Adding CPL filter to Blackvue DR400G-HD II
There is no “standard” fitting CPL filter for Blackvue DR400G-HD II, so I decided to make my own.
I bought cheap CPL filter for GoPro for Aliexpress and modified it to “fit”.
The filter glass can be extracted from metal ring by un-screwing inner ring:
Notice I have already marked “top” with marker. To determine “top” I simply sat in the car with sun high and rotated the CPL filter (make sure you have front and back correct) so there is no glare.
Here is the glass out (make sure you keep track of top and front).
Test fit:
Since the filter was too large (it would interfere with windscreen), I decided to grind it into this shape:
Grinding is a slow process involving slow orbital sanding with water (P400 or so). Don’t rush it or glass will crack (or the inner filter melt).
Test fit post grind:
Glued with dab of hot glue:
Note: in hot climate I recommend replacing hot glue with quality double sided moulding (thick) tape, as once the camera gets to about 60-70’C the glue will soften and lens will slide.