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Windows 7: JPG files changing size on me

19 Dec 2010   #1
nailgunner

Windows 7 Home Premium 64 bit
 
 
JPG files changing size on me

I am at the end of a photo-editing project. I am going back and adding titles/descriptions to some of the pictures. Quite by accident I noticed that when I add a title Windows is changing the size of the file on me.

The change doesn't show until I leave the folder and go back in. Well, of course you're saying, you add some detail and it will increase the file size by a few kb. Unfortunately it is reducing the file of every one I'm doing this to. One example is from 305kb down to 267kb, almost 1/3.

I don't notice a change in the picture when I view it, but that isn't really the point. Why is it doing this and can I get it to stop?


My System SpecsSystem Spec
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19 Dec 2010   #2
mjf

Windows 7x64 Home Premium SP1
 
 

What editor are you using.
jpeg encoding is a lossy encoding algorithm. Every time you decode-edit-encode you will get some image degradation even when the maximum quality (low loss) re-encoding option is selected and the image file will generally be larger.
In your case you must have the re-encoding quality set lower or changed the resolution resulting in a smaller file size.
My System SpecsSystem Spec
19 Dec 2010   #3
nailgunner

Windows 7 Home Premium 64 bit
 
 

I'm done "editing". I was just using Windows Explorer to list the files, and add a "title" at the bottom of the screen where the file information (date taken..size etc) is listed.

I was aware of the issues with jpeg degradation but with over 10,000 pictures total file size was an issue.

While I am technically "editing" the file, I'm not editing the picture itself, so I am confused as to why Windows is reducing the size of the file on me. I'm not even opening in it a viewer, just changing data. It is doing the same thing if I right click on the file, go into properties and add the title there. It should not be appreciably changing the file size on me.
My System SpecsSystem Spec
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20 Dec 2010   #4
mjf

Windows 7x64 Home Premium SP1
 
 

I tried what I think you were doing and my jpgs increased slightly in size. I assume it was only writing some metatdata to the file.
My System SpecsSystem Spec
20 Dec 2010   #5
nailgunner

Windows 7 Home Premium 64 bit
 
 

And that's what I would have expected, a small increase, not a substantial decrease. I am going to play with it on an XP machine, because this wasn't happening early in my project. Something is happening that shouldn't be, and I need to stop it.
My System SpecsSystem Spec
20 Dec 2010   #6
nailgunner

Windows 7 Home Premium 64 bit
 
 

The XP did the same thing. Didn't decrease it to the exact same size, but pretty close. I kept a full backup on there so I could check the same file. It did update the size immediately as opposed to having to re-enter the folder on Windows 7, but that was about the only difference.

Because of size constraints to fit these on flash drives for relatives (lucky them), I did subject them to a batch size reduction with one editor, and I'm thinking now it may have caused some kind of instability with the individual files. Because I had some that were not reduced and I can add the title on XP with no size change, and on 7 with a small size increase.

Looks like I'm stuck with what I have. Any other thoughts would be appreciated.
My System SpecsSystem Spec
20 Dec 2010   #7
mitchell65

Microsoft Windows 7 Home Premium 64-bit 7601 Multiprocessor Free Service Pack 1
 
 

When you say "I did subject them to a batch size reduction with one editor,"
Did you use Adobe Elements for this by any chance?
My System SpecsSystem Spec
20 Dec 2010   #8
mitchell65

Microsoft Windows 7 Home Premium 64-bit 7601 Multiprocessor Free Service Pack 1
 
 

Just done a test. I just added a tag to an image that was 6.22Mb. Just the one tag and the file size is down to 5.83Mb. Can only assume that as soon as you hit "Save" further slight compression of the image takes place as it always does when using JPEG's. Also the degree of compression would be the same as the degree used in the first instance. My editor has a range from 1 to 12 so if you chose 9 in the first place this would be the standard for all subsequent "saves". Have just done the same exercise with a PNG image. No change in file size here. Much as I would expect as PNG is not a lossy format. No compression takes place when you save it. So I would conclude that what you are getting is normal for a JPEG! On normal monitors this would make no noticeable difference to the quality, only if you were doing high quality printing to the image maximum size would it notice and then you would probably use a non lossy format anyway.
Answer is, if quality really matters, if you can't shoot the original in a RAW format, use the highest quality JPEG you camera will go to and then save the image to PNG or TIF before anything else and stay in that format until the last minute before you save for the final time, even after adding your titles, tags etc, then save to the highest quality JPEG your editor will go to.
My System SpecsSystem Spec
20 Dec 2010   #9
nailgunner

Windows 7 Home Premium 64 bit
 
 

Quote   Quote: Originally Posted by mitchell65 View Post
When you say "I did subject them to a batch size reduction with one editor,"
Did you use Adobe Elements for this by any chance?
I used trialware programs from Nikon and Corel for the all of the actual editing. The bulk of the reductions were done with one of those 2 (don't remember which one). I did my last batch of reductions with a freeware program PhotoScape (no actual editing with it).

The first batch is decreasing in size a lot. The second batch is increasing in size a little.
My System SpecsSystem Spec
20 Dec 2010   #10
fimble

windows 7 ultimate
 
 

I think Mitchell65 has got it. If say, on the 1-12 scale, 9 was save and compress to 75%, if you renamed the same file half a dozen times and it was compressing to 75% of its original, your final image would be under 20% the size (quality) of the original (first) jpeg image. One reason I never touch them if I can help it! I'm sure its lossy bit is embedded in its metadata telling it to lose unnecessary bits every time.
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 JPG files changing size on me




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