What is HDR (High Dynamic Range) feature on my iPhone camera? In what situation should I use the HDR feature?

HDR (High Dynamic Range) is an iPhone camera feature in which the camera will take 3 photos in very short period of time when you press the shutter:

• Original photo - With exposure time calculated normally.
• Overexposed photo - With slightly longer exposure time to get better result for those darker parts of the photo.
• Underexposed photo - With slightly shorter exposure time to get better result for those brighter parts of the photo.

The camera then creates an enhanced photo by combing the best parts of these three photos. This enhanced photo is called HDR photo.

The overexposed photo and the underexposed photo will be automatically deleted. But you have the option to keep the original photo and the HDR photo.

Since HDR requires the camera to take 3 photos of the same subject and combine them into the final photo, the subject should stand still or moving slowly. Otherwise, the camera will not be able to combine them nicely.

So you should not use HDR to take photos of fast moving subjects.

The picture below shows the comparison of the normal photo and the HDR photo from iPhone cameras (source: iphonephotographyschool.com):

⇒iPhone Camera Modes

⇒⇒iPhone Camera and Photos - Frequently Asked Questions