lensboard

or lens board

[ lenz-bawrd, -bohrd ]
/ ˈlɛnzˌbɔrd, -ˌboʊrd /

noun Photography.

the usually removable front panel of a view camera or enlarger on which the lens is mounted.

Origin of lensboard

First recorded in 1890–95; lens + board
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019