Hey there!
Here are a few tips on how to get quality photos and video with your iPhone.
Tip 1: Using proper lighting
If you don't have a fancy light or the budget to buy lighting equipment, record your videos in front of a window during sunlight hours.
Here are a few of my favorite makeup lights that can also be used for filming and photos.
For the examples below, I used the Glamor Brilliant Vanity Mirror
Tip 2: Adjust or Lock your Exposure and Focus AE/AF
Here is a great example. The photo on the left is auto adjusted exposure that my iPhone chose. The right is with changing the AE/AF.
That's the only difference in these photos. Nothing else!
To activate the AE/AF lock, simply open the iOS Camera app and tap on the screen. Instead of tapping and releasing, tap and hold for 3 second, or until the yellow square flickers.
When you release, you should see an "AE/AF Lock" indicator on the screen.
This AE/AF Lock feature works with both photos and videos, including the Slo-Mo option in iOS 7.
Once the AE/AF Lock is enabled, you can frame your photo without losing the exposure and focus controls you set. To undo the exposure and focus lock, just tap on the screen once and it will be removed.
Take a look at why locking your exposure while recording videos will improve the quality of them!