Tiff is a lossless format for images. It is often used when images are digitised and they are the basis of everything that follows. When a scan is insanely great, an image may be compressed into a JPEG or another format. When an image was damaged or dirty it is necessary to restore the scan. This is best done from the .tiff file, because compressing changes the picture and it makes it extra difficult to do the restoration.
This is an example of a before and an after image of an illustration of a camera obscura from a seventeenth century manuscript that was restored by Durova. The original is from the Library of Congress, and they are a truly magnificent resource because they provide best quality tiff scans and this allows for quality restorations.
Best practice has it, that when you restore a picture you provide both the original and the restored version. This allows other people to have their go at a restoration if they think they can do better then a Wikipedia featured picture. The problem is that they cannot.
They cannot because as a collaborative platform for restoring images MediaWiki sucks. MediaWiki does not allow people to save tiff files and this is really sad because there is a fledgling community of people restoring all kinds of files. As best practice has it, the original file and the restoration are saved but in a compressed format and consequently, the files do not qualify as the basis to get an even better result.
With the great cooperation with organisations like the Bundesarchiv, we are in a great position to entice archives to provide us on request with full size original scans that need to be restored. We would restore these images to their former glory and everybody is a winner.
It is beyond a doubt that the restoration work done by our volunteers looks smashing. But to impress the people from archives, the technical quality has to be as good. Restorations that are compressed just do not cut it.
Providing tiff support in MediaWiki improves the appreciation of the restoration work and, it makes MediaWiki a platform that can be used by the people who collaborate on these restorations.