Backing up JPEGS without compression and loss

[angieq]

I have a lot of JPEGS which I want to backup to an external hard drive or two . My son says that all software used to back up compresses the JPEGS. Is there any truth in this and is it possible to retrieve images backed up which are identical in size to the original without loss? I have noticed that all the copies of images that I have made on my HD lose quality when copied. Is there any way of cloning the exact image other than shooting storing them in RAW? Most of my previous images were not shot in RAW - they are only Jpegs.

[Jim Poor]

Simply backing up images doesn't compress them. Copying images doesn't cause a loss of quality unless you're doing it wrong.

[zenandzen]

If you have a file called myNewPic.jpg and you copy it and paste it to a new location, it will be identical to the original - no loss.

JPG files only 'throw away' information when you save or 'save as' in an editing application.

Let's say you open a file called myNewPic.jpg.
You may have made some modifications to it - adjust the contrast and a slight crop.

When you go to save it, it will throw some detail away to make the file size smaller - each time you save.
If you save it as a new file name, let's say myNewPic2.jpg , then you will keep the original intact and have a newer, slightly less quality but modified file saved.

TIFF is a lossless format and if you are worried you could make .tif copies of your .jpg files for storage but they are a larger file size.

[Jim Poor]

Originally Posted by zenandzen

If you have a file called myNewPic.jpg and you copy it and paste it to a new location, it will be identical to the original - no loss.

JPG files only 'throw away' information when you save or 'save as' in an editing application.

Let's say you open a file called myNewPic.jpg.
You may have made some modifications to it - adjust the contrast and a slight crop.

When you go to save it, it will throw some detail away to make the file size smaller - each time you save.
If you save it as a new file name, let's say myNewPic2.jpg , then you will keep the original intact and have a newer, slightly less quality but modified file saved.

TIFF is a lossless format and if you are worried you could make .tif copies of your .jpg files for storage but they are a larger file size.

Absolutely correct. It's important to add, however, that the difference when re-saving a JPG file at high quality settings is infinitesimal in terms of what can be seen in print or on screen.

[vsa]

Originally Posted by Jim Poor

...infinitesimal...

Fancy words. ..had to look it up.

But yea copying shouldn't decrease quality nor have I heard anything about backing up doing it either. You should ask your son about the source of his backup information.

[autofocus]

I think some backup programs that come with external drives will have an option to compress files in order to optimize the available space, so there might be some truth to what your son is saying. However, it should be an option, and probably not the default setting.

[kirbinster]

Data compression is very different than image compression. When you use data compression programs like winzip or winrar they use what is known as lossless compression. Jpeg compression is lossy compression where you loose data.