degradation of digital images

[Gary Majchrzak]

upfront warning: I'm admittedly not up to speed on this subject!

do digital images degrade?

if so... what's the best way to preserve them so they last the longest?

 

[Dino]

Well it depends a little bit on the type of degradation you're talking about. If you're wondering if the actual file will degrade over time just sitting on a hard drive like an old cardboard box stuffed in the attic - no. The media it's stored/written on can degrade, this is especially well known with media like DVDs, even "archival" quality DVDs can degrade in just a matter of years and unfortunately when they do it's typically when you need the backup file off of them. That is why you should always backup to multiple types of media and even more important, have backups off-site just in case of disaster.

Another side of this though is file type, certain types of file types like .jpeg for instance will degrade from constant overwriting/saving, this is why file formats like .jpeg are not recommended to be used as your editing copy but instead to do your editing in a loss-less file format then convert to something like .jpeg when you're complete.

If Beerguy sees this I'm sure he'll post, he's written some good things on backing up files.

 

[Jacob D]

Gary,

A digital image is a file on a drive, like any other file. Loss of data is on the only sort of degradation that can occur - but - drive failure will (usually) result in complete loss/corruption of the file (unless it can be recovered); I wouldn't consider that degradation of the file.

Loss of data due to image compression is the only real world sort of degradation I can think of. File formats that use lossy compression (jpg for example) discard some data each time the file is saved, thus reducing the image quality in a controlled sort of way. Some resizing programs have a similar effect; data is selectively discarded to reduce the file size while doing it's best to keep the image quality intact. Also some image hosting sites degrade the image quality via similar means. Examples of that - Face Book is terrible for hosting images. Flickr is one of the better ones but even there enough compression is used that I can tell a difference between my original and the hosted image immediately (in most cases).

This is why you should always keep your original images archived and save copies for the web etc... It's also why people tend to recommend working in lossless formats such as RAW, TIFF, PSD, etc... the last step is to export the file for the web.

 

[IslandCrow]

Good info in both responses. I attended a seminar awhile back and one of the subjects talked about (briefly) was the degradation of CDs and DVDs over time. I can't remember specific numbers, but tests have been done, and the time period for data loss was not very long at all. I was quite shocked. Hard drives, on the other hand, short of defects and externally induced file corruption issues are very survivable long term. Keep my pictures backed up on two hard drives (one internal and one portable) as well as an online backup system. As for the 1s and 0s themselves (i.e. the picture file), there's no danger there, except the loss of data Jacob & Cody talked about with compressed file formats like jpegs. But even with those, you can copy them to other locations as often as you want without a loss of data. It's just when you open up the file in an image editor and re-save it (whether you did any actual editing or not) that you may eventually see some degradation in the image itself.

 

[Gary Majchrzak]

thanks for enlightening me!

 

[lemec]

I'd hate to see your pictures of the purple carpet and clown degraded Gary...I still use them as a screen saver form time to time.

 

[ducklabdad]

Print them and store prints in an archive file as well, not in a frame exposed to light. Depending on ink, paper construction exposure etc.. many questions about how long prints will hold up as long as they are not exposed to the elements. Just another form of back up.