For most Android and iPhone users, the most interesting announcement that came out of Google I/O last week was Google Photos. The cloud service side of Google Photos was carved out of the Google+ Photos component. Google also released free apps for Android and Apple iOS (iPhone and iPad) to automatically upload photos from mobile devices as well as display and manage photos. Note that the Photos component for Google+ still exists and has at least one capability not available in the new service. But, we’ll return to this later.
Google Photo gives you unlimited storage space if you are willing to limit photo resolution to 16 megapixels and video resolution to 1080p. You do have the option to store at higher resolutions, but the storage counts against your Google Drive quota. Note that you have to make this resolution choice the first time you set up the Google Photos app on Android or iOS. This limit should not affect most phone and tablet users today. However, photo and video recording resolutions have increased tremendously over the years. And, even today there are phones like the Lumia 1020 that can record 41-megapixel images (although Google does not provide a Photos app for Microsoft Windows Phone).
I configured three phones to upload a total of around 8,000 photos to test Google Photos. Here’s what I found.
Source : http://www.extremetech.com/mobile/206990-google-photos-unlimited-storage-for-free-with-a-few-gotchas