Focusing system SX-70: Split-circle vs Ground-glass

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 2 and 3). Recomposing the image after focus is often necessary to achieve the desired framing (Figure 4).

Ground-Glass Focusing
In the early SX-70 type models the focusing screen was standard without the split-circle rangefinder. Focus was 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.