Leon Warnerke (26 May 1837 – 7 October 1900) was a Polish civil engineer and inventor in the field of photography, independence activist, revolutionary and successful forger.

Małachowski was born in the Kobryń district of the Grodno Governorate in the Russian Empire to Julian Malachowski and Theophilia (née Jakubowska).

After the collapse of the uprising, the police, on the orders of general M. Murawjow, issued an arrest warrant for Małachowski with a reward of 10 thousand zlotys, as a result of which he was forced to flee the country.

Because the sensitive gelatin emulsion had no paper backing, the orange window had to be replaced in this model with a tiny alarm bell triggered by an electrical contact being made through the perforations, which sounded after each frame moved to the appropriate point for taking a photo.

Warnerke's achievements include the sensitometer,[8] the first effective means of measuring plate speed, developed in 1880, which in the following year was recognized as a standard by a special commission and became the basis for standardisation in the field of photosensitive materials.

[4] Apart from his inventive and entrepreneurial activity, Warnerke maintained contacts with other designers and inventors in the field of photography,[9] as well as with photographic organizations and societies in various European countries.

In the 1990s a previously unknown archive of Warnerke's correspondence, forgeries, and personal documents was discovered by workers demolishing a building in London.