Forums
New posts
Articles
Product Reviews
Policies
FAQ
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Menu
Log in
Register
Install the app
Install
Forums
General Discussions
Switcher Hangout (Windows to Mac)
Data transfer: Images degrading...any ideas?
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="walkerj" data-source="post: 534824" data-attributes="member: 9385"><p>This, is absolutely correct. Also, you cannot necessarily trust whichever tool of the OS (Get Info, ls -l, etc.) to tell you the exact number of bytes in any given file. You can, however, trust that anything that straight up copies a file (Finder drag 'n drop, UNIX cp, mv, etc.) and backup programs will make a bit for bit exact replica of the original file to the target media. If this were not the case, any executable program would be immediately corrupted and no longer executable, or worse executable but with unpredictable errors.</p><p></p><p>Most operating systems (Mac OS included) perform continual copy operations, file moves, memory page-outs and the like in the background without intervention, shuffling gigs of data around per month with flawless accuracy. Believe me, if something were to go wrong there, you'd know it pretty darn quick as the system would fall ill, and eventually be unbootable/unusable.</p><p></p><p>Now, compression of images is a whole different issue. Copying one jpg file from one media to another isn't going to do anything to the image quality, as everything is replicated bit for bit, <strong>compression</strong> and all.</p><p></p><p>It is the compression that is the bug-a-boo of image quality. Every time you load a .jpg image into an image editor and save it, <em>even with the same quality level of compression</em> it is going to get irreversibly compressed a little bit more. The only time this does not happen is if you load the file, say, from the camera on which it was taken and save it in a non-compressed format. Non compressed formats are like .tiff or Photoshop's .PSD format. </p><p></p><p>This is why when I take pictures off of my digital camera, any picture that I load up to work on with Photoshop is subsequently saved in native .PSD format, regardless of how much bigger it makes the file. Only if I need it to be compressed for the usual reasons (emailing, posting on a web site, etc.) will I save to .jpg, and I do not consider the resultant jpeg to be anything but a disposable one-off version of the image. Images in .psd format can be reloaded and edited with no loss in image quality a<em>s long as they are not saved in a lossy compressed form.</em></p><p></p><p>So anyway, to conclude. What has probably happened is the mechanism you've used over time to shuffle these image files around has introduced additional, even if minute, compression artifacts. Standard operating system copy utilities will not, and cannot introduce compression to files of any type, image or no.</p></blockquote><p></p>
[QUOTE="walkerj, post: 534824, member: 9385"] This, is absolutely correct. Also, you cannot necessarily trust whichever tool of the OS (Get Info, ls -l, etc.) to tell you the exact number of bytes in any given file. You can, however, trust that anything that straight up copies a file (Finder drag 'n drop, UNIX cp, mv, etc.) and backup programs will make a bit for bit exact replica of the original file to the target media. If this were not the case, any executable program would be immediately corrupted and no longer executable, or worse executable but with unpredictable errors. Most operating systems (Mac OS included) perform continual copy operations, file moves, memory page-outs and the like in the background without intervention, shuffling gigs of data around per month with flawless accuracy. Believe me, if something were to go wrong there, you'd know it pretty darn quick as the system would fall ill, and eventually be unbootable/unusable. Now, compression of images is a whole different issue. Copying one jpg file from one media to another isn't going to do anything to the image quality, as everything is replicated bit for bit, [B]compression[/B] and all. It is the compression that is the bug-a-boo of image quality. Every time you load a .jpg image into an image editor and save it, [I]even with the same quality level of compression[/I] it is going to get irreversibly compressed a little bit more. The only time this does not happen is if you load the file, say, from the camera on which it was taken and save it in a non-compressed format. Non compressed formats are like .tiff or Photoshop's .PSD format. This is why when I take pictures off of my digital camera, any picture that I load up to work on with Photoshop is subsequently saved in native .PSD format, regardless of how much bigger it makes the file. Only if I need it to be compressed for the usual reasons (emailing, posting on a web site, etc.) will I save to .jpg, and I do not consider the resultant jpeg to be anything but a disposable one-off version of the image. Images in .psd format can be reloaded and edited with no loss in image quality a[I]s long as they are not saved in a lossy compressed form.[/I] So anyway, to conclude. What has probably happened is the mechanism you've used over time to shuffle these image files around has introduced additional, even if minute, compression artifacts. Standard operating system copy utilities will not, and cannot introduce compression to files of any type, image or no. [/QUOTE]
Verification
Post reply
Forums
General Discussions
Switcher Hangout (Windows to Mac)
Data transfer: Images degrading...any ideas?
Top