This article explains how to keep pictures in their original format on iPhone, instead of transferring them to iCloud. Remember that in this case the photos will take up more of the device's internal memory.
Steps
Step 1. Launch the iPhone Settings app
It features a gray gear icon. It is normally visible on one of the pages of the Home.
If you can't find it in Home, try looking for it in the folder Utility.
Step 2. Scroll down the "Settings" menu and choose the iCloud item
It is the first option of the fourth group of items that makes up the "Settings" menu (immediately below the "Privacy" tab).
If the iPhone is not synced with your iCloud account, you will need to enter the corresponding Apple ID and password
Step 3. Tap the Photos item
It is the second option listed in the fourth section of the "iCloud" menu.
Step 4. Disable the "iCloud Photo Library" slider by moving it to the left
Make sure it is white in color and not green.
Step 5. Select the Download and Keep Originals option
It is listed in the second section of the menu. A small blue check mark will appear next to the item indicated. At this point the photos will be stored in the iPhone memory, rather than in iCloud.