Aside from buying filters, be sure to look into using your white balance setting on the Spark. It does make a nice difference. it is where you set for sunny or cloudy and other options.
Can you get a PL/CP with ND 16 or 32? I'm planning on taking my spark with me on a cruise in a few months and I'm sure when I'm in port there will be a lot of sunlight and a lot of water reflection...so I'm guessing I should probably have both? Or is that not the case?
I have a set and love what Polar Pro does and their quality.
The reason for the multiple pieces is for us film geeks to get closer to the 180° shutter speed (so 30fps needs a 1/60 shutter).
This yields a more “cinematic” look.
Without an ND filter (on a sunny day), the iso is low and the shutter speed is high to compensate for the brightness. This high shutter speed reduces the motion blur usually associated with Films.
Polar Pro has a free app that helps you select what filter you need based upon current situation and camera readings to get the desired look.