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Do Digital files degrade with time ?

Harry Joseph , Jan 31, 2011; 04:03 p.m.

Not sure if it's me or my computer or both, but some photo files that have been saved on my computer seem to have degraded with time. Is this possible ?


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Walt Flanagan , Jan 31, 2011; 04:06 p.m.

Degrade in what way? Everytime you edit a JPEG and resave as a JPEG you will lose a little bit of quality. If you don't edit the file then the file should not degrade unless your hard drive is having problems.

Matt Laur , Jan 31, 2011; 04:08 p.m.

Degraded in what way? Generally speaking, a file is intact, bit for bit, or it's corrupt. There's rarely any middle ground. And data errors - if your editing/display software can still show you the picture at all - would likely manifest themselves as flawed spots, or odd looking chunks of pixels, sometimes in a pattern.

Yes, various data storage devices can show errors over time. The optical media decays, the magnetic patterns on the hard disk start to lose their clarity ... but this won't really show up as images that just don't look as good as they used to. If that's the case, you're probably looking at images that you prepared on older software, or while using a different display, or while editing in a different color space/profile, and which don't look the same to your more experienced current eye, or on more recently configured equipment.

Regardless, make a point of refreshing your backups. It's just a bunch of ones and zeros! It's easy, and it gets cheaper every day to but gargantuan disk drives.

Michael Axel , Jan 31, 2011; 05:14 p.m.

Up. It's called digital rot. The very early digital files I shot (before the DSLR craze) are toast. Entire CD's (the best you can buy at the time) cannot be read.

There used to be a program (which I haven't seen for awhile) called something like Sure Write (I think I'm slightly missing it, but Right Way sounds like a large format film back). It would rewrite your ones and zeros, keeping them moved around and charged on the disc so they wouldn't lose their magnetism.

Tudor ApMadoc , Jan 31, 2011; 05:17 p.m.

If you are archiving to DVD's make sure you use gold ones that are listed as archival
An article on this : http://adterrasperaspera.com/blog/2006/10/30/how-to-choose-cddvd-archival-media

Charles Webster , Jan 31, 2011; 05:17 p.m.

@Michael, your problem isn't digital rot, it's CD rot. So long as the file can be read without corruption, it will remain the same as when it was recorded.

Any solution that claims to refresh your files is just churning your HD and further fragmenting your files, which leads to degraded drive performance, but not "digital rot"


Hector Javkin , Jan 31, 2011; 05:35 p.m.

Aside from the rare corruption of a file, which is likely to make it unreadable, the typical degradation of image files occurs when it is stored as jpeg, read, and saved (not merely closed.) Each instance of saving a jpg file brings about a new lossy compression, so that the image will degrade visibly if enough reads and saves are performed. This does not happen when lossless compression such as tif is used.

The more likely thing is not that a stored digital image gets worse, but that our opinion of it gets better. When we look at it again, and it hasn't changed, we become convinced that it has degraded.

Michael Axel , Jan 31, 2011; 05:50 p.m.

My early CDs were Gold.

Tudor: Your article is very good, but also properly states that gold is not the be-all, end-all. It is more than just buying gold discs.

Charles: "So long as it can be read without corruption, it will remain the same as when recorded." Yes... and the difference is? I agree, it can fragment files, but you can also unfragment them and reorder them.

Hector: I disagree. Any bit that is recorded can be destroyed. TIF files (thought my favorite for storage because they are a textual representation of an image), are not exempt from "rot".

Here is another good reference for bit rot/data rot: http://en.wikipedia.org/wiki/Bit_rot

barry goldberg , Jan 31, 2011; 05:54 p.m.

I know that for myself, photos that I thought were quite good 10 years ago when viewed on today's much better monitors, they don't look very good. I wonder if the OP is experiencing the same or is it something different.

And a note for those people who use CDs or DVDs for archival. I would immediately make sure that you multiple copies, preferably both on hard drives and in the cloud (meaning on the web). CDs and DVDs can get lost and will burn in a fire.

Dieter Schaefer , Jan 31, 2011; 06:01 p.m.

Each instance of saving a jpg file brings about a new lossy compression, so that the image will degrade visibly if enough reads and saves are performed.

I keep reading this - and I want to add that if the JPEG is saved at the maximum quality, I can't detect any degradation and the file size is not reduced, indicating that no further compression has taken place. I just saved the same file ten times and the file size actually slightly increased. I do certainly agree that if a JPEG is saved and re-saved at less than maximum quality, then a visible degradation is observed already after a few saves - of course depending on the actually quality setting used. I save all my JPEGs at maximum quality and reduce the size only when required, for example, to post in a forum or on certain photo sites with size restrictions.

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