I have drone video that was shot in 4k, I have to pull some stills out of it and have it re sized to 851 x 315 and 900 x 300. What is the best way to resize the iamges with out loosing resolution?
There is no such thing. You will of course lose information since data gets interpolated. There are ways to minimize the loss of information by employing adjustments and effects just as well as doing the resizing in multiple steps to control specific aspects, but reducing a 4k shot to 10% of its size is always going to look like a crappy webcam photo, no matter what.