Focusing System SX-70: Ground-Glass vs Split-circle

Ground-Glass Focusing
Focus is set by adjusting the focusing wheel until the image on the viewing screen appears uniformly sharp (Figure 1 and 2). This method provides an unobstructed view of the scene, which can simplify composition and evaluation of focus across the entire frame. Many photographers favor ground-glass screens for their consistency and lack of visual interference. This type of focusing screen was standard in early SX-70 models.

Split-Circle Focusing
The split-image rangefinder is specifically intended as a focusing aid and not for composition. Focus is achieved by rotating the focusing wheel until the two halves of the split image align seamlessly into a single, continuous line (Figure 4 and 5). Recomposing the image after focus is often necessary to achieve the desired framing (Figure 6.