Will the photos saved in my computer lose quality over time?
No. This is a defining quality of digital storage — every value is discretely rendered to a number, and those numbers are recorded. This means that digital files can be copied an infinite number of times without introducing error, and that as long as nothing happens to the underlying storage, the file itself will always be the same.
It is possible for the media (like hard drives or DVD) to develop errors, which render numbers unreadable (or occasionally flipped from one to another) — but this can actually be checked for and verified. Make sure that you have backups, and verify those backups periodically.
Unlike printed media, digital photos will always remain exactly as they were when saved, unless the media holding them becomes corrupted for some reason. However it's easy to store a large number of copies at various datacenters in order to alleviate the problem.
That being said, digital photos do tend to lose quality in terms of our subjective perception. As camera tech develops our idea of what a "good photo" is will change as well. Perhaps in 100 years all pictures will work as interactive Harry Potter-like 360-degree panoramas and modern day shots will look the same to our descendants as photos from 1917 look to us. Or maybe the very idea of taking pictures will become obsolete as we'll all be able to relive a moment by plugging ourselves into a Matrix-like simulator. So while your photo might win you a Pulitzer today, it might as well be an archaic museum relic to future generations.
No, they do not loose quality.
But you could consider the following points, besides the fact that any storage medium may fail in doing its job (becoming corrupt, defect or any thing likes this):
- While copying files from one medium to another errors can occur and destroy some bits or bytes. But it is possible to prevent this error.
- Computer technology changes. A computer in 20 years may not be able to read your hard drive.
- Display technology changes. Example: a display with high pixel density makes a picture looking sharper than on an older display with less pixel density.
- People change their way they look at an image and what they think is good quality or not.
- File formats of today may not be supported in the future. I don't expect to have a RAW converter available for todays camera in 30 or so years on the operating system and the photo software compatible of this time.
... list may be extended to some more points.
While not that common nowadays, a hard drive may fail, a data disk can get degraded or scratched, plus, there are some infrequent occasions when file may be subject to bit rot.
This is typically circumvented by keeping several copies of data, as well as implementing error correction processes on hardware level
The main issue is uncaught data degradation -- if you do not touch a file for a long time, you have no idea if it is still valid.
My personal approach is to keep everything on a RAID-1 or mirrored hard drives, but if I were earning my living by photography, I would invest in a way of storing more copies and checking them frequently.
Really, if you downvote based on the idea of digital being perfect, you forget that nothing exists without medium.
Even film negatives tend to detoriate with time. So does whatever medium you store your digital photos on.
And possibly you haven't had the old CD-Rs die on you by having their outer layer come off in flakes.
However, the OP specifically said that he was asking about photos saved on his computer -- which is currently either a magnetic hard drive or a solid state disk. Both of which can and will detoriate.
And I speak from experience of doing digital preservation for a national library, so we had this question discussed and researched for quite some time before selecting the tools.
I may have read past it, but I did not see anyone issue the caveat that if you repeatedly open compressed images and re-save them, you will incrementally degrade the image. Lossless image formats – raw, psd, tiff – will not degrade with repeated saves/overwrites.
CDs are not an archival media and can definitely degrade over time as is happening with some collections.
The biggest risk in long term digital storage is drive failure or obsolescence of the media type. For example, it would be quite a project to retrieve images from an old Syquest disk, Iomega Zip disk or Jazz cartridge!
No. As stated above, that's the whole point of 'digital storage and photography'.
As long as the image is kept on good devices and in good conditions, the file will remain the same. However, over time, files might get corrupted or get errors which will result in rendering problems. But that's not something you should think about since almost all media storages nowadays will not develop this kind of issues.