Why does the size of an image decrease with drag-moving?

Question

Hello, I have found myself in a quite frustrating situation.

I have been sorting out my files and I noticed that some of the photographs decreased in size when I drag-moved them from the folder "My pictures" to another folder on my local HDD.

For example: One of the photographs used to be 5.18MB and is now 4.73MB. The resolution stayed the same: 6000x4000 and when I compare the photos (I did a back up before moving the files around) in windows photo viewer there is no difference whatsoever. Also when I check the colour graph in Adobe Lightroom there is no difference in files.

Why did the file size decrease? Should I be worried or is it possible that some useless metadata dissapeared when I drag-moved the photographs?

Thank you

Juan

Answer 1

I really doubt that what you're seeing has anything to do with file compression (and no, those folders are NOT normally compressed folders).

What sort of picture files are you using?  I ask because JPG files, which are very commonly found photo files, are already highly compressed, and even if you had moved them into a compressed folder, the size likely wouldn't change much.

I don't think you should lose metadata (especially not 450 KB as in your example) by moving between directories on the same partition (i.e., the same "letter drive"), but right-click on the files, select Properties, and then look at the "Details" tab to see if there is any missing information.

You're probably seeing some artifact related to the way NTFS stores data.  See, for example, https://technet.microsoft.com/en-us/library/hh148159.aspx and for even more detailed (and largely incomprehensible) information read discussion linked there (“The Four Stages of NTFS File Growth”).

Answer 2

Thank you for your reply!

In the link that you inserted is says "The compression state of an NTFS file or folder is controlled by its compression attribute." I don't quite understand: how does one tell whether or not the folder is in a compressed state or not?

Answer 3

I am moving it within the same hard drive.

Answer 4

Hi

Are you moving it within the same hard drive or are you moving it to another hard drive within the same machine?

Let us know.

Cheers

Answer 5

Hello Juan,

If you move a file from a folder to a compressed folder, the file size will decrease, but this won't directly affect the contents or the quality of the picture/file.

For reference, you may check our support page for more information:

Zip and unzip files

Effects of Compression on Moving and Copying Files

Let us know if you require further assistance.

Regards.