The Becquerel process is the only variant of the daguerreotype process. While the Becquerel process was introduced in the 1840s by Alexandre-Edmond Becquerel, it was not popularly used in the 19th century. The process is more commonly used by contemporary practitioners. The major differences between Becquerel’s process and the standard daguerreotype are the plate is sensitized only with iodine fumes and it is “developed” under a red filter in bright sunlight. Development may take up to two hours. Becquerel plates often have a slight blue colorcast.