Something that disappointedly me with the new Google photos service is that it doesn't keep your original photos (and is quite sneaky about it)
What it offers is storage of photos up to 16 megapixels. Thats great right? Most phones (and cameras) have less than that. So what's the catch?
The problem is that Google photos compresses your shots using a lossy algorithm, so data is lost. The resolution is not affected, but individual pixels are. See attached image for an extreme example of compression artifacts.
Ever wonder why photos look bad on Facebook? Heavier compression than other sites. And photographers being obsessive about detail, lossy compression, of any kind , is bad.
I'm sure Google photos uses algorithms at a level most users won't mind, but its not really a true backup of your photos. The higher tier does promise to "store your photos and videos exactly as you captured them."..... For a price.
edit: the compression level according to Google engineer :
"free storage is 16MP at JPG90, which is higher than the Lightroom default of 75. :)"