May 29, 2015

How much does compression by cloud storage providers degrade image quality?

When I store my photos in the cloud on Google Photo, Google compresses the files, sometimes by a dramatic amount. Even so, the images still look pretty good...or at least as “pretty good” as they did when I took them. How much is this aggressive compression actually degrading the image quality of files stored in the cloud?
To add to what Jim already said, there was a post on Reddit recently where Redditor Freshyfunk posted an album with images before and after compression by Google. It was amazing how little difference in image quality there was between the two, despite significant compression.

See for yourself here:
JPEG Compression Test: Google Photos vs. JPEGmini

"Google’s method is remarkably good. The reduction in image quality is almost imperceptible, yet it manages to nearly cut the file size in half. On the other hand, JPEGmini manages to eek out an extra 40% compression with only trivial image degradation. Most remarkable of all, though, is that by combining the two–Google and then JPEGmini–it doubled the compression even of the already-compressed image!

Of course, the double-compressed image has the most notable degradation of image quality, but even so, it is so minor that, I think, it is still almost certainly unnoticeable in large photographs."
Answer this