How to back up the photos of the camera to the mobile hard disk when traveling without a computer?

If you want to back up the photos in your mobile phone camera, you can find your photo folder in the folder and copy it to otg's external hard disk. At present, mobile phones generally support otg, but some mobile phones can only support fat32 format and cannot recognize ntfs format. If it's a camera, there's nothing to do. Ordinary cameras do not support otg. Now many cameras can transmit photos wirelessly, so,