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I have been using Google Photos as a way of backing up my photos. I noticed recently that they store two versions of any photo I upload, one with the original name of the file, say, IMG_20140328_1143.jpg and another IMG_20140328_1143-edited.jpg. The original one is 2.0 MB, while the "edited" version is around 1.5 MB.

I did not do any editing so it is strange to me that this is happening. Upon using ExifTool to analyze them, the megapixels and image width height are all the same, so I am not sure why there is a difference in file size.

Is the edited version a more lossy version of my original?

I have included the readouts from ExifTool. The first is for the original, the second is for the edited one. Any help would be greatly appreciated!

The Original:

ExifTool Version Number         : 10.55
File Name                       : IMG_20140328_1143.jpg
File Size                       : 2.0 MB
File Modification Date/Time     : 2017:04:04 22:15:58-04:00
File Access Date/Time           : 2017:10:24 01:07:47-04:00
File Inode Change Date/Time     : 2017:10:24 00:45:24-04:00
File Permissions                : rwxr-xr-x
File Type                       : JPEG
File Type Extension             : jpg
MIME Type                       : image/jpeg
Exif Byte Order                 : Big-endian (Motorola, MM)
Make                            : LGE
Camera Model Name               : Nexus 5
X Resolution                    : 72
Y Resolution                    : 72
Resolution Unit                 : inches
Software                        : Google
Y Cb Cr Positioning             : Centered
Exposure Time                   : 1/100
F Number                        : 2.4
ISO                             : 241
Exif Version                    : 0220
Date/Time Original              : 2014:03:28 11:03:10
Create Date                     : 2014:03:28 11:03:10
Components Configuration        : Y, Cb, Cr, -
Shutter Speed Value             : 1/100
Aperture Value                  : 2.4
Exposure Compensation           : 0
Flash                           : No Flash
Focal Length                    : 4.0 mm
Flashpix Version                : 0100
Color Space                     : sRGB
Exif Image Width                : 2448
Exif Image Height               : 3264
Interoperability Index          : R98 - DCF basic file (sRGB)
Interoperability Version        : 0100
GPS Version ID                  : 2.2.0.0
GPS Altitude Ref                : Above Sea Level
GPS Img Direction Ref           : Magnetic North
GPS Img Direction               : 183
Compression                     : JPEG (old-style)
Thumbnail Offset                : 650
Thumbnail Length                : 10320
XMP Toolkit                     : XMP Core 5.1.2
Creator Tool                    : Google
Image Width                     : 2448
Image Height                    : 3264
Encoding Process                : Baseline DCT, Huffman coding
Bits Per Sample                 : 8
Color Components                : 3
Y Cb Cr Sub Sampling            : YCbCr4:2:0 (2 2)
Aperture                        : 2.4
Image Size                      : 2448x3264
Megapixels                      : 8.0
Shutter Speed                   : 1/100
Thumbnail Image                 : (Binary data 10320 bytes, use -b option to extract)
Focal Length                    : 4.0 mm
Light Value                     : 7.9

The "Edited" One:

ExifTool Version Number         : 10.55
File Name                       : IMG_20140328_1143-edited.jpg
File Size                       : 1467 kB
File Modification Date/Time     : 2017:04:04 22:15:58-04:00
File Access Date/Time           : 2017:10:24 01:10:56-04:00
File Inode Change Date/Time     : 2017:10:24 00:45:24-04:00
File Permissions                : rwxr-xr-x
File Type                       : JPEG
File Type Extension             : jpg
MIME Type                       : image/jpeg
JFIF Version                    : 1.01
Exif Byte Order                 : Big-endian (Motorola, MM)
Make                            : LGE
Camera Model Name               : Nexus 5
Orientation                     : Horizontal (normal)
X Resolution                    : 72
Y Resolution                    : 72
Resolution Unit                 : inches
Software                        : Google
Y Cb Cr Positioning             : Centered
Exposure Time                   : 1/100
F Number                        : 2.4
ISO                             : 241
Exif Version                    : 0220
Date/Time Original              : 2014:03:28 11:03:10
Create Date                     : 2014:03:28 11:03:10
Components Configuration        : Y, Cb, Cr, -
Shutter Speed Value             : 1/100
Aperture Value                  : 2.4
Exposure Compensation           : 0
Flash                           : No Flash
Focal Length                    : 4.0 mm
Flashpix Version                : 0100
Color Space                     : sRGB
Exif Image Width                : 2448
Exif Image Height               : 3264
Interoperability Index          : R98 - DCF basic file (sRGB)
Interoperability Version        : 0100
Image Unique ID                 : 43935602c77d9f620000000000000000
GPS Version ID                  : 2.2.0.0
GPS Altitude Ref                : Above Sea Level
GPS Img Direction Ref           : Magnetic North
GPS Img Direction               : 183
Compression                     : JPEG (old-style)
Thumbnail Offset                : 726
Thumbnail Length                : 4356
XMP Toolkit                     : XMP Core 5.5.0
Creator Tool                    : Google
Image Width                     : 2448
Image Height                    : 3264
Encoding Process                : Baseline DCT, Huffman coding
Bits Per Sample                 : 8
Color Components                : 3
Y Cb Cr Sub Sampling            : YCbCr4:2:0 (2 2)
Aperture                        : 2.4
Image Size                      : 2448x3264
Megapixels                      : 8.0
Shutter Speed                   : 1/100
Thumbnail Image                 : (Binary data 4356 bytes, use -b option to extract)
Focal Length                    : 4.0 mm
Light Value                     : 7.9
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Is the edited version a more lossy version of my original?

Not necessarily. JPEG compression has a lossy stage (DCT, subsampling) and a lossless stage (Huffman). It's possible that Google is just optimising the Huffman stage.

To compare the two images, you can load them both into an image editor and look at the symmetric difference. I know that Gimp can do this (paste the second image in a layer, set layer mode, merge down, view histogram), and I'm sure Photoshop can too.

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Yes, this is due to JPEG compression/re-compression.

The EXIF data and the resolution will stay the same and you may not even notice a difference in image quality.

Every lossy compression method will decrease image quality, even if the file size does not change.


Answer

Yes, the edited version of you image has been re-compressed by Google and is a more lossy version of your original image.

  • Thanks! How can I quantify just how much loss was incurred? Is there certain software that would do this? Thanks! – user321627 Oct 24 '17 at 11:20
  • Unfortunately that's not possible. See also this answer: stackoverflow.com/a/2024971/3556403 – oa- Oct 24 '17 at 12:51
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    Do you know, or just assume, that the second version has been recompressed (in a lossy way) by Google. For JPG files, file size itself does not necessarily correlate with the level of compression. – jarnbjo Oct 24 '17 at 13:56
  • I just assumed. I do not know for sure. I am wondering if there might be a way to tell. – user321627 Oct 26 '17 at 4:00
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Your files are different. They are either saved with a different software, or with different parameters.

When you look at the thumbnail length, that is 10320 for the first one and for the second one 4356. That already accounts for a little bit of the difference :=).

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