Default [Q] Q: Save Camera Video/Pics to OTG USB as default

Howdy

I have an LG G2 and would like to take a picture/video with the camera and have it save to the otg usb instead of internal memory.

Tried google but not much joy. I would like to use the default camera app as it can do 4k video but a third party app will do for pics.

Any help appreciated.