There is a large number of photos surviving from the 19th century. Most of these are portraits, which are generally very formally posed unsmiling subjects. Great historical records. Unfortunately many of these are extremely "noisy" with dust and scratches. Editing them can be a very time-consuming job.
Here is a portrait of a couple (husband and wife? who knows?) dating to around 1855. First is the unedited version (well, not entirely unedited - it was cropped and the brightness and contrast adjusted) and then the cleaned-up version. This was the work of probably 8-10 hours.
Purists may decry altering 19th century photographs like this, and experts will probably scorn my meager Photoshop skills. Still, I think the result isn't too bad.