I posted some of these earlier but moder(nish) camera phones deserve far more credit than is currently given. I used Huawei P20 Pro with self-made 3D-printed filter holder housing real filter threads and arca-swiss tripod foot during my latest winter photo trip quite a lot:
CL-Pol filter used with Smooth Water -program. One minute stack (phone stacks at very high shooting rate and combines almost in real-time).
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And some material from last summer. This one with 720nm Infrared filter and a CL-Pol filter (yes, the filter holder is properly sealed to prevent light leaks) and 30 second exposure. B&W sensor in use.
ND400 filter used here with CL-Pol. 5 seconds.
ND1000 (? maybe, don't remember) with CL-Pol. 30 seconds.
Deep Red B&W filter, CL-pol and ND64 filter. B&W sensor.
720nm Infrared filter, CL-Pol. B&W sensor.
I do wonder why Huawei did the stupid thing and left B&W sensor out of their modern phone models? The 20MP tiny B&W sensor is capable of IQ of B&W converted APS-C camera RAW file. They should throw away the ultra wide angle 40MP sensor from Mate 30 Pro and replace it with ~1-inch B&W sensor which would put most FF cameras to shame in B&W game.