First of all, you need to connect your iPad with your computer using the data cable which comes in the box. Connecting the iPad to your computer will bring up iTunes automatically. If it does not start automatically, you can do it manually from your computer.
After you do that, you need to remove the photos which you want to unsync from the synced photos folder. Remember, you do not need to delete the photos from your hard drive. Just move them away from the synced pictures folder.
Go to the main window of iTunes and click on your iPad from the left navigation menu. Click on the Photos tab which appears in the main window.
Clicking on the Photos tab will show you all the folders that you have synced with your device. Select “Selected albums, Events and Faces, and automatically include” option. This will ensure that you only sync selected folders with your device. In the bottom window, you will see a list of all the folders present in your computer. Check the checkmarks next to the folders names which you want to sync. Make sure you also check the folder from which you want to remove the photos.
After this, click on the Apply button. The changes will be applied and the photos you removed from the folder on your computer will also be removed from your iPad.