The long term archival of analogue data, especially photographic images, has to minimize at least two risks: 1) the total destruction of the image e.g. through fire or water, and 2) the intrinsic decay of the images through the natural aging of the medium has to be slowed down as much as possible. Both risks can be minimized by appropriate storage (location of storage, fire protection, climate control etc.). As a consequence of optimal storage, access to the archived images will be very restricted and difficult. Further, the intrinsic decay of the images due to aging cannot be stopped totally but only be slowed down. Since all copying of analogue media such as photographs, film, video etc. always and inevitably imposes a decrease in quality, the original has to be preserved. It is usually possible to interpret analogue media such as photographs without the use of technical means. Metadata such as image description, photographer, timestamp etc. are often recorded together with the image on the same media (e.g. notes on the back of a photograph) and which therefore can not be separated from the image and the risk of loosing the connection of the metadata with the image is usually very low.• With respect to long term archival and compared to analogue data, digital data has completely different properties:• Given the proper procedures, digital data can be copied infinitely oft (infinite number of generations possible). The “original” and the “copy” are identical and cannot be distinguished. Therefore the notion of an “original” looses its sense in the digital domain.There is no slow decay in the digital domain. Digital data either can be read completely, or there are errors reading the data that invalidates the whole data set. In order to recognize the occurrence of read errors, special algorithms (“checksums”) have to be used.What reasons may cause the loss of data within the digital domain? The following short overview is especially targeted to the problems of long term archival where not only the image object alone but also the information about the object, the metadata, has to be stored. For digital archives, another difficulty arises: digital media can only be read and interpreted by using technical devices. A computer tape looks the same to the human observer if it's empty or if it contains images, texts or other data. A vault with 10'000 CD-ROMs that are not labeled is almost without value if there is no other information available. The consequence is that improper archival strategies can lead to a fatal loss of information at many different levels. If only at one of these levels information is lost, the whole archive will be virtually worthless or at least the value will be diminished severely.