Lens manufacturer Cooke has increased its workforce of assembly technicians by 25% since 2011.

The Leicester-based firm said the growth was a direct response to the increasing demand for PL glass.

Cooke Optics chairman and owner Les Zellan said: “As digital cameras with PL mounts, such as the Alexa, Red and Sony F65, have grown in popularity, so we have seen demand increase exponentially for our lenses.

“In order to keep pace with demand we have expanded our workforce and created several apprenticeships which, in times of recession, is a remarkable and gratifying thing to be able to do.” 

Both series of Downton Abbey were shot with Cooke S4 lenses (pictured).