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Category: New Questions

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Photography Question 
Hans Abplanalp
BetterPhoto Member

member since: 2/8/2005
 

Backing Up JPEGs


If I transfer (save), for example, 500 JPEG images from my PC to an external hard drive, I assume that I will have a slight loss of quality. If I then shoot another 50 images, download them to my PC and then transfer (save) all 550 images onto the same hard drive (because I don't remember which ones are new), do I then lose quality on all 550 or only the new 50? In other words, does the hard drive skip over what is already saved on it and only add the new 50 images? Thanks for any help.
Hans

4/1/2012 1:23:15 AM

 
Christopher J. Budny
BetterPhoto Member
chrisbudny.com

member since: 10/3/2005
  You only experience JPEG degradation when you open the file in an editor and save it again. So if you have all your finalized JPEG's sitting on your C: drive, and you merely drag-and-drop a copy of those files onto your external drive (doing a File-Copy, for instance in Windows Explorer), you're not opening/resaving each one, and not introducing "new file compression" that a File...Save As... JPG does each time you save.
So If you file-copy (not Save As) 500 files to external, and then later file-copy those same 500 plus another 50 new, as long as you're doing a file copy, and not a Save As, you should see no newly-introduced image degradation. You should also get a prompt asking if you want to write over the 500 existing images or not.
You can confirm all this easily in a test: Take a finalized JPEG you already have on C:, and file-copy it into say, 5 other folders... then go look at the properties of each file (such as using Windows Explorer to see the properties.)
Then, take a different JPG, open it in your editor, save as JPEG to a different folder. Close it. Go open that newest JPEG (not the original) in editor, save as to yet another different folder, close it; do that 5 times, and compare the File Properties of the original to the File Properties of the 5th Save As version. When I do that test, the Save As (i.e., opening, saving, closing each "next generation file" repeatedly), I see slightly-decreasing file sizes for each file, ranging from 387,401 bytes (original) to 386,096 bytes (last Save As file) indicating each successive Save As is doing more compressing each time.

4/1/2012 6:39:31 AM

 
Hans Abplanalp
BetterPhoto Member

member since: 2/8/2005
  Many thanks Christopher, that's very helpful.

Hans

4/1/2012 10:53:44 PM

 

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