Definition of pentaprism in US English:



  • A five-sided prism with two silvered surfaces giving a constant deviation of all rays of light through 90°, used chiefly in the viewfinders of single-lens reflex cameras.

    • ‘Pros, from what I've read, is that mirror pentaprisms are lighter, can be made smaller to save space, and are cheaper to manufacture than glass pentaprisms.’
    • ‘I was just looking through my junk bin over the weekend and I found that I have a number of pentaprisms taken out of 35mm SLR cameras.’
    • ‘DSLR (Digital Single Lens Reflex) by definition have optical viewfinders, usually consisting of a instant-return mirror and a pentaprism.’