This plate is much thinner compared to the prism in Bolex cameras, increasing the likelihood that lenses designed for other cameras (such as non-reflex models) will be compatible with Pathé cameras. However, even the small difference caused by diffraction in this thin plate makes the distance markings on those lenses inaccurate for the Pathé camera. Due to the plate, the lenses are calibrated to a 17.58 mm distance instead of the 17.52 mm standard for C-mount lenses. Even this 0.06 mm difference is enough to prevent achieving sharp focus in the same plane when using lenses designed for other cameras, compared to lenses specifically designed for Pathé cameras. Focusing on digital cameras is much simpler, especially with zoom lenses, as you can zoom in, set the focus (which is easier to achieve in close-ups), and then zoom out to the desired framing. Some cameras even feature a focus-assist function, allowing you to press a button to temporarily magnify the image for precise focusing. This is particularly useful when using fixed-focus lenses instead of zoom lenses. However, in fiction filmmaking, especially when using older equipment, zoom lenses are typically avoided because prime lenses (fixed-focus lenses) offer superior quality in terms of aperture and reduced aberrations. Without the ability to zoom in for close-up focusing, achieving precise focus through an optical viewfinder becomes more challenging. A practical technique is to focus on a sharply defined, high-contrast edge. For example, you can use a package with contrasting text, like a chocolate wrapper. If you need to focus on an actor's eyes, have them hold the package next to their eyes and use the contrasting text to set your focus. When using older zoom lenses, extra caution is needed, as not all zoom lenses maintain focus while zooming out. This issue is more common with lenses that are adapted for a camera mount rather than designed specifically for it. Some cinematographers feel uneasy relying solely on their eyesight for focusing, so they prefer to measure the distance from the desired focus point (usually the eyes of the actor) to the film plane – just as they’ve seen professionals do in behind-the-scenes footage. 45