GalleryRAW

Simple and fast gallery application with support for raw image files from Canon, Nikon, Sony and Fujifilm cameras. Raw Image Viewer. Android app for importing and viewing raw images from professional cameras on your tablet or smartphone. Acts as a file manager supporting .cr2, .cr3, .nef, .raf raw formats including viewing and transferring files from/to usb storage connected via hdd/ssd disks, camera flash drives connected via usb adapter.
This is the first and so far the only android application with which you can quickly view in full-screen mode by swiping through raws and then select only a few photos from several hundreds or thousands of photos in folders from a camera flash card connected via usb to your tablet or phone. And then copy only those selected photos to your phone or tablet's internal memory or flash card, and then delete the rest of the raw photos you don't like from your external usb to make room for new shots.