There are different ways to back up iPhone. The common way is utilizing iTunes or iCloud. However, if you need to selectively back up iPhone, try below solution.
Leawo iTransfer is the one you need. As a perfect iOS data management tool which can support all iOS devices, Leawo iTransfer covers all kinds of iOS data like photos, videos, music, SMS, etc. Transferring speed and safety are not the problems you need to worry about, since Leawo iTransfer can perfectly take care of them. Now I am going to show you how to back up iPad to external drive via Leawo iTransfer.
Step 1: Download and install Leawo iTransfer on PC
From
https://www.leawo.org/itransfer/, you can simply download Leawo iTransfer. Install it on your computer and launch it. Connect your iPad to your computer with USB cable. Your device will be automatically scanned and all information will show up in the right part of the window.
Step 2: Transfer your photos to your computer via Leawo iTransfer
Choose "iPad > LIBRARY > Camera". Select the photo you want to transfer or click the photos with holding "Ctrl" to multiply select. Then click the arrow icon in the bottom right corner.
Step 3: Transfer your photos to the external hard drive
In the following pop-up dialog, check the box besides "Save to folder". Click "Change" to select where you need to save your photos in your computer. Connect your external hard drive to your computer. Copy the photos you already transferred from iPad to the external hard drive. This is how to back up iPad to external drive via Leawo iTransfer.
You may worry about that your computer is laptop, indeed, you can use iTransfer to realize
backing up iPad to laptop without any difficulty.
For more details, check:
How to Back up iPad to External Hard Drive on PC and Mac Respectively